I have heard he said that while the Yaks were initially suspected of being less reliable than western counterparts before they got there, it turned out they were quite reliable and were operational generally more often than western types were in very cold conditions. He related the Russian method of adding gasoline to the cold, thick oil to thin it out, and then it evaporated as the engine warmed and was gone by the time they were ready for takeoff, and removing and sleeping with batteries so they stayed warm. He also doubted they would be at the same reliability rate in warmer weather because the radiators were seemingly sized for colder conditions, but they never really found out for sure as it was usually cool when compared with desert, south Pacific, SE Asia, etc.
They REALLY liked the Russian guns as they hit hard and had very good destructive power per projectile. Only a few hits were needed for real damage.
The Russians were friendly but not exactly forthcoming. That is, they wouldn't share any information they weren't ordered to share or give most rations or equipment / supplies that weren't specifically allotted to the group. That included blankets, etc. So it could easily happen that the Soviets might be quite comfortable in the cold while the French were quite freezing. They DID share knowledge of ways to get around the muddy tundra when required to do so, and they could be counted on to share Vodka semi-often in small quantities. Everyone wanted to see pictures of anyone back home, same as us, particularly girlfriends / wives, and shared same.
He related that the Germans they saw were mostly just soldiers who were not really intersted in being there, but the Russians, if they caught some, were somewhat brutal, probably in retalliation for Germans sometimes doing the same to Soviets on the way into Russia. He said it was NOT a good thing to captured during WWII by the Soviet side. He did not mention any prisoners that their own group took, and we nobody asked about that at the time.
Like being on ANY active front, it was great leaving and going home, but he had no desire to ever go back and see the places where they served at that time.
Treat all the above as second-hand information.