I am not entirely sure what you mean by "positive", and that is somewhat subjective.

There were certainly long term effects as the dynasties established by his generals following his demise lasted for centuries and spurred on the Hellenistic Era which was both a period of growth and advancement for Hellenism and lead to new and distinct cultures emerging in the Near East and North Africa. Over the next 3 centuries most of Alexander's Empire found itself within the sphere of influence of one or another of the kingdoms named the successor states. Perhaps, most obviously demonstrating the widespread influence of Hellenism, was that Koine Greek became the most widely spoken language throughout the Mediterranean (particularly the eastern Mediterranean), Middle East and North Africa even after the Roman Empire reached its height and the spread of both Greek cultic practices and the conflation of deities such as Aphrodite with Near Eastern equivalents such as Ishtar or Astarte and the spread of Hellenised foreign deities such as the Egyptian goddess Isis and her consort Serapis whose worship lasted until the widespread adoption of Christianity in the Roman Empire.

Ptolemaic Egypt just so happens to be my favourite topic so I am going to focus on that and mostly neglect the albeit fascinating and deserving Seleucids.

Following the death of Alexander in 323 BCE his empire saw itself partitioned and rivalries between competing factions known as the Diadochi saw the various empires carved out of Alexander's conquests at war. Ptolemy I Lagides became the Satrap of Egypt following the death of Alexander, by 310 BCE Alexander the Great's posthumous son Alexander IV had died and circa 304-5 BCE he became Pharaoh of Egypt as well as assuming the Greek title of Basileus as well as taking control of Cyrene (in modern day Libya), Cyprus, Syria and Judaea. The latter three would remain a point of contention between the Lagides and the Seleucids for centuries to come however, and Syria and Judaea (often referred to collectively as Coele-Syria) along with the island of Cyprus would change hands more than once during the course of the aptly named Syrian Wars.

What I will mainly focus on though, is not as much the borders that were drawn or the wars over them but the cultural, economic and societal legacy of the successor states. When it comes to Egypt, Michel Chaveau sums up the implication of Macedonian conquest quite satisfactorily when he states that

In the hands of a dynasty foreign to its traditions, its language, and its religion, Egypt was nevertheless to experience a period of economic prosperity, political power, and intense intellectual and artistic activity. For the first time in their history however, the Egyptian people were now confronted by a genuine social and cultural challenge: the settlement on their soil of a large number of immigrants, heirs to a different and highly advanced civilization who would try to impose their own way of life and modes of organization as the dominant model.

Ptolemaic Egypt for the most part fits the standard of a colony and its rulers, to varying degrees, treated Egypt as an estate more than a nation. Greek became the official language and all court documents were issued in it, but it seems that Demotic Egyptian remained the primary language for most of the population and there are a surprising amount of papyri dating to the Graeco-Roman period in Demotic script. The organization and administration of Egypt was largely unchanged by the Ptolemies and highly bureaucratic system of governance that remained the same for the simple reason that it was ideally suited to the geographic, economic and societal quirks of Egypt.

Society under the Ptolemies

Regional differences, mainly the distinction between Upper Egypt (the more rural southern region of the Nile Valley) and the more cosmopolitan Lower Egypt (the Northern Nile Delta region) which were further separated into smaller districts called Nomes, with each nome having its own capital were already a part of cultural landscape prior to Macedonian conquest.

For the most part, Greek and Macedonian settlers were concentrated in Lower Egypt. That is not to say that Upper Egypt did not have a significant Greek presence however, in fact the city of Ptolemais Hermiou was founded as the capital of the Thebaid region by Ptolemy I and was said to be comparable to the Egyptian city of Memphis in size. Ptolemais was similar to many other Greek poleis in so far as it had its own constitution and elected local officials and magistrates.

Alexandria, capital of all of this and home to perhaps 300,000, centre of commerce and culture, saw residents, merchants, and scholars from across the "civilised" world forced into close proximity and as a result it developed its own distinct and inarguably mixed character, seperate even from the other Greek colonies and port cities in Egypt which is why the term "Alexandria next to Egypt" and travelling between Alexandria to Egypt were used in Antiquity. The term Alexandrian is likewise applied to citizens of the city, cultural and intellectual products, and due to the notoriously hot-tempered disposition of its people, to several civil wars and large riots.

The situation in Egypt and in particular, Alexandria is often compared to a melting pot but this comparison is somewhat of an oversimplification and it ignores the many class distinctions and cultural differences between the three predominant ethnic groups, Greeks, Egyptians and Jews, with Greeks at the top of the social pyramid and Egyptians making up a disenfranchised majority and Jews occupying their own niche. Even with that there are some distinctions between Macedonian settlers and other Hellenes although this distinction became gradually less important with time as the citizens became unified by a common Hellenic identity in their new home, and this identity appears to have broadened even further to include some Egyptians as well but I will get to that later. A relatively large number of immigrants, students, merchants and mercenaries hailed from elsewhere in the Helladic world, Asia Minor, Western Europe, and even India adding to the religious and ethnic diversity of the city.

At first, the army was entirely comprised of Macedonian and Greek hoplites and supplemented by a large number of expensively retained and outfitted mercenaries but in the 2nd Century BCE Ptolemy IV was forced to find a large supplementary source of conscripts to withstand the invading forces of Antiochus III (a member of the rival Seleucid dynasty) in Coele-Syria, and by training and outfitting some 30,000 Egyptian hoplites to complement his army was able to soundly defeat his enemy at the Battle of Raphia in 217 BCE. However, arming and training a large force of Egyptians contributed to the secession of Upper Egypt upon his death in 205 BCE following the economic struggles and unrest in the wake of the war. While Egypt was torn apart by internal struggles, Antiochus III took the opportunity to invade and annex Coele-Syria in 200 BCE.

It would be inappropriate to mention the secession of Upper Egypt without providing proper context. Prior to Alexander the Great's conquest Egypt had been a satrapy of Achaemenid Persia for 10 years but before that it had been conquered by Persia in 525 BCE and revolted and regained its independence in 404, an independence which lasted until 342. Alexander, who negotiated the Persian satrapy's surrender and took pains to respect Egyptian tradition and was crowned Pharaoh in Memphis was viewed not as a conqueror but a liberator. However, when Alexander appointed Kleomenes of Naukratis as satrap who demanded arbitrarily heavy taxes from the very priests and upper class Egyptians which had supported Alexander as Pharaoh attitudes quickly soured. Under Ptolemy I and II Egypt was relatively stable and the healthy economy allowed for peaceful relations between the various groups, however the ineptitude of later successors, wars in Asia Minor and internal struggles over the right of succession would contribute to the dynasty's decline around the close of the 3rd century BCE.

From 205 to 185 BCE Upper Egypt was in open rebellion against the Lagides and two Egyptians were proclaimed Pharaoh in these regions, Hurwennefer from 205-197 and his successor Ankhwennefer from 197-185 held more than 3/4 of Egypt until the insurrection was violently and firmly suppressed by Ptolemy V who had made peace with Antiochus III and married his daughter Cleopatra I (Not the famous Cleopatra, but her great-great-great-great grandmother) and was then able to focus on regaining his lost Egyptian holdings. The famous Rosetta Stone was a stele issued by the priesthood at Memphis circa 206 and it states that Ptolemy V offered forgiveness on debts and on certain taxes owed and lightening of other taxes, offered gifts of grain and gold to the temples and priesthoods, paid bonuses to the soldiers in his army, forgave prisoners, banned the practice of forcing free boatmen to serve in the Navy, allowed those who were involved in the rebellion to retain their property and return to their homes, and his defeat of rebels in the south of Egypt among other things.

Adding to the unrest that cropped up sporadically throughout the Ptolemaic Period was the bloody legacy of civil wars between rival factions within the royal family which often extended into riots and coups within Alexandria itself and ultimately contributed to Egypt's decline in political power and status as a client-kingdom to Rome in the 1st Century BCE as monarchs reached out for support from Roman allies and as a result, Rome became increasingly involved in settling these disputes while a combination of military might, growing territories in the East and economic ties brought Egypt ever more into the sphere of Roman influence.