Fellas, given that the P-38 is my favourite, I might be biased plus that being in haste, have read only the first 2 pages here. But, a few notes:
1. It is quite odd to claim that the P-38 was much more complicated to handle. Not exactly so. I encourage to take a look at the P-38J/L pilot manual vs. F6F-5 manual. In combat, a P-38 pilot needs to control throttles, rpm and mixture. Since in combat the mixture has to be auto-rich, that can be forgotten. All cooling flaps are automatic, as are the turbochargers (no need to operate turbos via a separate control). In the case of the Hellcat, the pilot needs to handle throttle, rpm, cowl flaps, intercooler flaps, oil cooler flaps and supercharger lever (3 positions). So, which is actually the more complicated to handle?
2. Complicated maintenance. Was it much more complicated than the P-47? The British AFDU report states that the routine maintenance is very easy with excellent access to armament, engines etc. (except for radio).
3. The very same report speaks very positively about its manoeuvreability, despite the very high wing-loading.
4. Critical Mach number. Yes, definitely much lower than that of the Mustang. But, compare to the much-praised F8F and then, the difference isn't that great.