Chuck, IMHO you've hit the nail exactly on the head.... assuming that the saw engine starts and runs properly, 95% of *cutting* performance is the chain. Of course, there are MANY different chain designs, and only some of the larger more commercial saws can use the more aggressive designs, plus, the more agressive they are (in general), the more kickback-prone they are, so many retailers (big boxes) will not even sell the really good-cutting chains or saws wearing them! I think this may be one reason that many folks swear by Stihls, because the dealers are a bit more liberal with selling more agressive chains on them.
I have found that by taking the depth guides down to a little more than the typical 0.025", even the super-safe anti-kickback chain performance can be increased quite a bit.
- Jay