Ascetically I love this airplane but I have always wondered how much of the P-39/63's rep on the E. Front was due to hype. The Russians needed all the help they could get and for a Russian pilot to be critical could have meant a lot of trouble for him.
And the US used lend lease for all the good publicity they could ring out of it. If we were going to give away fighters why not ones that were conveniently in production and we didn't really want?
No doubt the Soviets used the planes with some success - but so did we, not only in the Pacific but in the Med.
Soviet Union wanted as many P-39s they could get, they thought it was clearly better than P-40, US and GB pilots mostly had an opposite oppinion. IIRC 3 out of the 5 Soviet top aces got most of their kills while flying P-39.
Juha