You act like devs can just push a magic button and make games run faster, add more polygons and add more effects. It doesn't work like that. In terms of architecture the alpha kits are 180 degrees different than the beta and final kits. Performance doesn't always scale linearly (is that a word?) with processor speed. In fact, the performance may even drop in some cases! We're talking an entire architectural shift going from alpha to beta.
It's not like PS3 devs who showed "games" developed on 6800's in SLI or 7800 GTX (in the case of the latter it, gives them 75% of PS3 performance). In fact, the most impressive Xbox 360 game at E3 was Gears of War. It looked leagues above everything else. We wondered why. We soon learned that the game wasn't developed using alpha kits, but rather using *gasp* 6800's in SLI. Epic did this because they wanted immediate results and they wanted to reach around 80% of their target performance right away. The best looking Xbox 360 games you will see are the games that started YESTERDAY...not two years ago. I think some of you guys are being unfair and just downright unreasonable. I mean, Gears of War is proof in the pudding as far as what happened.