Obryn
Hero
Maybe it was due to the supplements, but I found the biggest difference was tone between 3.0 and 3.5.
3.0 "felt" lower-powered, overall. Most creatures were kind of "low-balled" or whatever, to accommodate characters with somewhat average stats, like the 25-point buy. 3.5 more or less acknowledged that everyone would have a higher power level, and upped the creatures as a result.
Like I said, this may have been related to splatbooks, but there you have it.
-O
3.0 "felt" lower-powered, overall. Most creatures were kind of "low-balled" or whatever, to accommodate characters with somewhat average stats, like the 25-point buy. 3.5 more or less acknowledged that everyone would have a higher power level, and upped the creatures as a result.
Like I said, this may have been related to splatbooks, but there you have it.

-O