1) Escape artist works differently. When you use it to escape out of a grapple, you "ignore" all size modifiers to the grapple check. So far example, a huge creature normally gets a +8 bonus to his grapple checks. If you use escape artist, he no longer gets this bonus...making it a much more attractive option to compensate for those big critters.
2) The tumble mechanics are different. Its now your tumble check versus an opponents attack roll to tumble without suffering AOOs. Also, in 3.5, if you attempt to tumble through an opponent and fail you get stopped. In AE, even if you fail you get past him, you just take the AOO.
3) TWF is slightly different.
So for example with a longsword/shortsword and the TWF in 3.5 you would have a -2/-2 to attacks. In AE with just the ONE TWF feat, its +0/-4, meaning you suffer no penalties on the normal attack. Now, there is an ambidexterity feat in AE, that reduces the penalties all the way to +0/+0, that's right, you can have TWF without penalty in AE.
