I recently thought of another implication that is a result of E6's level cap. It seems that it would make playing a human much less desirable. With only 1 level based abiltiy score boost and less powerful ability score boosting items, the +2 to an important stat for playing a half-orc or dwarf (for example) seems much more valuable. You are only losing one feat, and you will get that back your first 5K of experience after 6th level. Have you noticed less human PC's in your game? What do you think of having the ability score boosts at 3rd and 6th level instead of at 4th and 8th? I know this is tweeking, but it really doesn't change the game that much.