This is rather long one, so before I write anything else, here is the summary:

tl; dr: Tito was central figure in Yugoslavia and held practically absolute power, so Tito gets credit for everything that was good between 1945–1990 (creation of social state, industrialization, creation of universal health care, relatively open borders), but at the same time is held responsible for bad things (dictatorship, police state, mass murders after WWII, political prisoners). A On top of that he was a bon vivant and womaniser.

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Tito being incredibly popular and loved within Yugoslavia and admired by other Eastern Europeans

Tito was extremely opressive and Yugoslavia was a policestate, sometimes said to be on the same level as the USSR with killings, etc.

I can't give you an answer, I can only try to elaborate those pictures a bit.

As for supporters:

First, you must consider how Tito got to the power. He was a rather successful leader of partisan guerillas against Nazi Germans and their collaborators, and by the time the war ended he was de facto ruler of Yugoslavia. It seems he was charismatic enough even without this warrior aura, which boosted his reputation. His army counted hundreds of thousands of soldiers, some of which were mobilized (even forcefully), some were opportunistic and wanted to end the war on winning side, but others were either communists or people that were saved by partisans – they were given chance to fight back to Nazis and collaborators. Those were the people that were either targeted by Nazis (like Jews or political opponents), or they didn't agree with Nazi policies. There was also lot of supporters that haven't joined partisans, but gave them food, shelter, clothes, etc.. Large parts of that population groups became hard-line Tito supporters after the war, and many of them and their family members are fond of him even today.

Second, there was that split with Stalin, where Tito successfully broke relations with Stalin effectively ending Soviet mending in Yugoslav affairs and thus reducing their sphere of influence. That basically enabled him free hands in both internal and external policy. He was independent of either Blocs, but still could cooperate with both of them. That policy led to foundation of the Non-Aligned Movement. This apparent independence gave rise to Tito's prestige abroad as well as home. And because Tito was independent of USSR he could proceed somewhat more liberal approach in internal matters.

Third, being a communist Tito initiated campaign of industrialisation, which meant employment for many young people from rural areas, who started to move to towns and cities. As socialist state Yugoslavia was trying to provide housing for those people, which created entire city quarters of commieblocks. One could relatively easy afford apartment there (of course there were privileged like Army and communist party members who got it easier than others) Those people that solved their existential problems because of this policies are now rather old, but still many of them credit Tito for that. On top of that, Yugoslavia gradually developed universal health care, which is also often connected to Tito in popular perception.

Fourth, one of the main differences between Yugoslavia and other Socialist states is that Yugoslav citizens could travel abroad, especially after Ranković fell from power in 1966. That meant that many otherwise hardly employable young people (usually from peasant background and very little if any schooling) could leave and find the job elsewhere, most often in Germany. Those people were very grateful for that possibility because they were able to rise from poverty and became rather well of citizens when they returned home. That wasn't possible in other communist countries, so Tito was seen not only as courageous and powerful enough to successfully stand to Soviets (which other communist leaders mostly didn't succeed) but also reasonable enough to let his people seek their fortune elsewhere (unlike Ceaușescu)

Finally, there was a cult of personality which was meticulously constructed by Communist party. It ensured that Tito is seen as infallible, as only true leader. Indoctrination started at school age, even before, through education system, and, well, something of that image of Tito kind of stick with many of them. On top of that he liked a luxury, was a womaniser, looked rather well, dressed nice, and was seen as both man's and ladie's man. All of that makes Tito seen in rather positive light by many. You can hear things like “Look how many leaders came to his funeral! These blokes today that call themselves statesmen – even their own mothers wouldn't come on theirs.” and such.

On the negative side:

Well, he while he was all that what was mentioned above, he also was a dictator, which means you had all the things that goes with dictatorships: police state, political prisoners (especially notorious was Goli otok prison, but there were many others), opposition wasn't tolerated, Army had a great influence on civilians, secret services were notorious for tracking and murdering dissidents, and so on.

His actions immediately after the WWII are dubious at best. After notorious Bleiburg repatriations lot of people were executed because they ended war on the wrong side without exemption for those drafted against their will or innocent of crimes committed by collaborators (mostly by Ustaše, but also Chetniks and Germans as well as others ). There were Kangaroo courts, mass executions, and politically motivated processes. Mass graves from that period are founded till this day (Macelj, Barbara's pit, and many others. Those that weren't immediately killed were subjected to extremely rough treatment, and were often sentenced to longish prison terms, usually with hard labour. Many of those people were released till 1960's, but they were broken men most often than not.

Also, lot of people were subject to ideologically motivated processes because of their anticommunist views, or were just seen as class enemy, be that private enterprisers or well off peasants. And you didn't need to have much to be considered class enemy. Process of collectivization was based on theSoviet model for the few years after the war, there was forced nationalization, and private property was restrained. Many were beaten, jailed, and/or left impoverished during those processes. Those particular policies ended or undertook considerable modification after Tito-Stalin split, but effects and consequences stayed.

Members of collaborator forces had very limited access to employment, especially in public services,and that often extended on their families. If you were born in wrong family you could say good bye to state sponsored scholarships (and there weren't any other), which were often necessary for getting higher education.

Tito resolved national question in Yugoslavia (I just don't have time to get into that) by simply putting it under the rug. All nations were to be considered equal, as were all the republics. Macedonians got their own Republic, Kosovars got autonomous region, Bosnian Muslims were recognized as nation. Tito is still popular in those regions because of this facts. However, Serb and Croatian nationalism, even in most benign form (financial, see Croatian Spring for example) was heavily suppressed. That, a top of everything else, left some Serbs and Croatians, but others also rather uncontented, which created set the stage for dissolution of Yugoslavia.

There are many more things, like tensions between more and less prosperous Republics, longish mandatory military service that made lot of young men resentful towards the system symbolized by Tito, but all of this is rather very long as it is, so be free to correct my mistakes, and ask if something isn't clear enough or if you like to know more, I'll answer if I can.

edit: typo, format, grammar, phrasing, missing words