I was thinking, the US has the reputation for not rushing combat systems into service, or at least the Army did, but early on the Pacific side of things, when the Wildcat was just on par or arguably worse than the Zero, the US Navy and Marine Corps had a fighter problem. In the air over midway and Guadalcanal they worked out tactics that allowed the wildcat to handle the Zero, and then much of the Japanese Navy's excellent pilots died at Midway, but there were some serious fight left in the Japanese, and it's combat prowess was not the F4Fs only limitation, range was a big one as well.
In February of 1942, the Corsair is rushed into the Solomons, and and are issued to a F4F squadron, and they are not given time to retrain they go into combat with only a few hours on the big fighter. Now look at the photo above, the list of problems with the Corsair or F4u-1 in the photo, it has the early bird cage canopy and lower cockpit, it still surely has the bouncy oleo struts, it probably has the shorty tail wheel. It does have the top cowl flaps pinned down, but many early ones didn't. This caused visibility problems for two reasons, one they stuck up, the second, they leaked oil onto the windscreen. Some problems the early birds like this had, but you can't see, the main gas tanks often leaked, enough to cause it to leak out of the top forward fuselage panels, but not serious enough to not fly combat missions in. I mean, after a half hour or so, the fuel level was probably below the leak area, so no biggie right? They also discovered a problem with the ignition system, that could cause it to cut out above 21k feet, this one got fixed before it flew combat missions.
The squadron that took them into combat first, took a beating, and I think only achieved a 1 to 1 loss ratio. It would be until units that had spent time training on the Corsair showing up before it would really start getting kills, and even then, the US Marines, and Navy land based squadrons had bad days. It was damage like the damage found in this photo that earned the corsair its reputation for being a tough aircraft, and there are a lot of photos of corsairs like this or with worse damage making it back.
In mid 43, after we had moved a little further up the Solomons Islands, the improved F4U-1A started to show up, with improved oleos, a longer tail wheel strut and improved tail wheel, the wing spoiler, new 2800s that were wet, and best of all the raised cockpit and improved semi bubble canopy.
Like this, though this still has the short tail wheel strut. It's a small myth that these problems caused it's removal from the Bunker Hills air group, they had been pioneers in solving the carrier landing problems, and had a full complement of brand new with all the fixes F4U-1A corsairs, but there was not enough corsair parts in the supply pipeline for the carriers to support them, so VF-17 took them to the Solomons to be land based, towards the end of the hot air days, and kicked some ass. There were still a lot of birdcage corsairs in combat at this point too.
The Corsair would of course go on to be used on carriers, both escort and fleet in the last year of the war, because they wanted more fighter squadrons to deal with the Kamikaze threat. Since the Corsair could do both Air to air and Air to ground well, with the -1D models, most carrier air wings put their dive bomber squadrons ashore, and took on a pair of Corsair squadrons. In some cases these squadrons were Marine units! By this point the Corsair was almost as tamed as a 2000 horsepower WWII fighter could be.
You could almost say this about the P-38, but I think it took combat use for them to really figure out what was wrong with it, more than teething issues.