The Spitfire went through many versions in WWII. It was always that little bit better than the best German fighters, except for 11 months between August 1941 when the Focke Wulf 190 first came out and July 1942, when the Spitfire Mk IX took to the air with a more powerful Rolls Royce engine. During that 11 months, the Focke Wulf was faster than the Spitfire at low and medium altitudes, though it could never turn as well, and was less effective at high altitudes, which limited its usefulness as a bomber escort.

The Spitfire had various weaknesses at different times during the war. In the Battle of Britain, Me 109 pilots could often escape by throwing their fuel injected planes into a steep dive. If the Spitfire tried to respond, the g-forces on the carburetor would starve the engine of fuel and the Spitfire could not keep up. The British pilots developed tactics (a twisting dive) to alleviate this, and a new type of carburetor was developed to eliminate the problem.

Later in the Battle of Britain, the Germans started armoring their bombers and fighters. The 8 machine guns on the Spitfire packed insufficient punch to get through armor easily, and it became harder to shoot the Germans down. (The Me 109 had 1 cannon and 4 machine guns). The Spitfire factories managed to redesign elements of the Spitfire and add cannon in 9 weeks, causing Lord Beaverbrook, who had ordered the change to lose 100 pounds, as he had bet they could not do it that quickly.

Probably the largest problem with the Spitfire was that it was a difficult plane to build. Especially the thin and elliptical wings,which were one of the main reasons for its speed and maneuverability.

Hurricanes were easier and faster to build, which is why there were more of them than Spitfires throughout the Battle of Britain.

The Spitfire was usually faster, and could always turn better, than any German fighter. It proved to be a hugely versatile airframe, which could be continuously improved and modified, especially with more powerful engines and weapons.

The Spitfire was a superb aircraft; that it could evolve through 24 variants, being in service with the RAF from the first day of World War II to the last and beyond is a testament to the design. Though highly subjective, it's generally regarded as a beautiful aircraft, which does it no harm in terms of public relations.

It's undoubtedly acquired near-mythic status, inflating its actual importance, though also a reasonable portion of associated myth-busting (the fact that Hurricanes shot down more German aircraft than the Spitfire in the Battle of Britain is reasonably well known).

A lot of enthusiasts fixate on marginal differences in performance between aircraft (or tanks, guns, or just about any piece of military hardware), sometimes known as "rivet counting"; I'll happily delve into minutiae myself (as elsewhere in this thread). It's seldom, if ever, the most important factor in a battle or war, though. Taking the Battle of Britain, it was a battle of attrition, the Luftwaffe trying to destroy Fighter Command, the RAF defending the country while preserving their strength in case of invasion. The Spitfire was important, a convenient shorthand to represent the Battle, but it was only one element. Dowding's command and control system, of which the Chain Home radar stations were a vital part (but only a part; like the Spitfire they can be a convenient shorthand for the whole), was essential to allow Fighter Command to assess and counter incoming raids. Manufacturing and repair were critical, and in this respect, as mentioned elsewhere, the Hurricane was easier to build and fix, though the British aircraft industry stepped up such that pilots became the limiting factor; pilot training, and developing pilots with basic training into efficient fighters, was of utmost importance.

As shown in e.g. Poland, even well trained pilots in completely outclassed aircraft stand little chance, some sort of parity with German fighters was important, but the performance of the Spitfire was not the decisive difference in the Battle. (There's a deeper and more contentious question over whether the Battle as a whole was even particularly important, considering the impossibility of landing and supplying an invasion force in the face of the Royal Navy, but that's a whole other issue.)

In terms of weaknesses, the Spitfire (like the Bf 109) was an interceptor par excellence, able respond at relatively short notice to get up to altitude to engage other aircraft. It was ideally suited to the Battle of Britain, or the siege of Malta, but one of the compromises was short range and combat endurance. As the war progressed and the threat to Britain itself faded, the Spitfire was less well suited to an offensive war, unable to escort bombers into Germany (the key role of the P-51 Mustang later). With the Luftwaffe less and less of a threat, especially after Operation Pointblank, there was less of a role for an air superiority fighter like the Spitfire. They were employed as fighter-bombers, mostly because there wasn't much else for them to do; the Hawker Typhoon was better known in that role, and could carry a heavier payload. Spitfires were also used for photographic reconnaissance through the war, making their greatest contribution to D-Day in that capacity.

The perfect aeroplane? The reason the war was won? No; as per the title of a Ben Goldacre book, "I Think You'll Find It's a Bit More Complicated Than That". As a starting point to look into things a bit more deeply, though, it's not a bad one.

The Spitfire has a special place in the hearts of the British, mainly because of its role in the Battle of Britain. It's also a stunningly beautiful aircraft, which helps a lot.

So an aircraft with such a ...fan-following, for lack of a better term...is always going to be seen through rose-tinted spectacles.

Having said that, an aircraft that first flew in 1936, saw continuous combat through WW2 and served into the 1950s clearly has something going for it.

Like any weapon system the Spitfire was good in some situations, not so good in others. As a short-range interceptor backed up by a decent warning system the Spitfire gave good service in the Battle of Britain. It also proved very useful over Malta, North Africa and Burma. The Spitfire was better than anything else the Allies had available so once Spitfires arrived in useful numbers, the Axis air forces started having to work harder ("Spitfires over the Arakan" is a good read to demonstrate this.)

Among other things, most of the other early-war Allied fighters were greatly inferior in performance to the BF109 and/or not so good at any kind of altitude. (The Hurricane's performance started falling off after about 15000 feet) The Bf109 had a performance edge over the Spitfire, until the two-stage Merlin/Griffon Spits arrived later in the war, but the Germans had to deal with a fighter that was manouverable and almost as fast.

The Spitfire was also turned into an effective high-altitude interceptor and a good photo-recon aircraft - PR Spitfires could reach Berlin and get back with the goods.

Later on Spitfires were turned into useful fighter-bombers although their vulnerable cooling system meant that they were never as effective as the more rugged P47. Which also carried more firepower. Then during the V1 offensive Spitfire XII and XIV squadrons proved very handy against doodlebugs.

In other areas Spitfires didn't fare so well. For instance, the Russians tried using Spitfires and weren't impressed. (They didn't like the P47 either. )

Spitfire Vs sent on offensive fighter sweeps during 1941-2 were hamstrung by lack of range and poor performance compared to what the Luftwaffe were flying at the time. The end result gave Luftwaffe experten some impressive high scores but otherwise don't seem to have achieved much. On a similar note, the first Spitfire squadron sent to engage Japanese fighters over Darwin lost a lot of aircraft due to running out of fuel.

The Seafire, meanwhile, was a lashup and had a fairly bad serviceability rate.

So the Spitfire was not a perfect aircraft by any means. The range was poor, the narrow, fragile undercarriage was a liability and sometimes it just wasn't the aircraft for the job.

When all is said and done, the Spitfire was the best the Allies had and it gave the Allies something that could take on the Luftwaffe, until the Mustang and Thunderbolt arrived on the scene. Even then, the Spitfire could give a good account of itself. Tellingly, several USAAF squadrons flew Spitifires.

Trivia time: The highest altitude dogfight in WW2 was between a JU86R and a pair of Spitfire IXs at 43,500.

Suggested reading: Norman Franks - Spitfires Over The Arakan David Isby - The Decisive Duel

Spitfire was not better than 109 which had better engine with fuel injection .. German pilots were more worried about lack of fuel than Spitfires..RAF was fighting a war in their home turf while Germans were behind enemy lines and had little time in British airspace many times they had to break engagements and flew back to France ..The battle was not fought under equal conditions. Everything about the Spitfire was associated with myth similar to King Arthur pulling the Excalibur from stone !