Man, the attitudes of some people on this game are sickening.
I fly at whatever altitude is optimal for the situation... If I'm going on an attack run, I'll stay at around 4,500 feet. If I'm going in for a furball, 7,500 feet. If I'm going on a bomber run, then at least 25,000 feet is necessary. If I'm going a long distance in a late-war fighter (P-51D for example), I'll go to 33,000 feet.
The low-altitude furballers in this game scream of "cowardice" when a pilot takes his Spitfire up to 15,000 feet... Yet if they weren't cowards, they'd engage said Spitfire at said altitude. The intelligent, calculated pilot surveys his surroundings and acts accordingly, using multiple tactics (BnZ, cherry picking, etc) rather than just one (turning as fast as you can). The advantages of altitude are very clear. What isn't clear is why many refuse to fly up there.
It might have something to do with patience (or lack thereof). It could also have something to do with the fact that most really don't know how to do anything aside from turning in tight circles in superior low-altitude fighters (Spit 5, Lavochkins, Yaks).
I think I've made myself clear... And for you bomber "pilots" who don't go above 2,000 feet, I'll say this: Learn how to fly the damn bombers up high where they're supposed to be.