I actually wrote the wiki entry on the Yak-7 a while back, not that I'm a super expert at it....
In a nutshell, the Yak-7 is the paragon of average....it is a combination of mediocre qualities that when put together make for a decent, but not dominating ride. The reason for this is that while the plane is not exceptional at anything, it's not horrible at anything either. It's stable, turns decently, climbs decently, has decent durability, okay acceleration, and effective but limited ammo.
Overall it's a fun, stable ride that can get the job done, but you don't have the Yak-3's built-in escape clauses so you have to be more aware of your circumstances and you can't afford to push a bad position. I like flying it for a challenge and to perk farm occasionally.
