Sorry this is a slow reply iroken22, I only just came back here now that I have the beta. Does this mean that Windows 7 is built on Vista, or did they re-write lots of code to make it faster? I don't mean to sound stupid, but I know nothing about code.
Everything is 'based on' what came before, since no company wants to or needs to start from scratch every time, or even ever after 1.0 really. Part two of your query, how much was left as was and how much was redone, is the huge variable. In my opinion, Vista wasn't broken, didn't crash, ran programs well, etc. I perceived it just got a bad rep for UAC, speed, hdw support, app compatibility, and such. All of those areas were addressed in W7, so time will tell. I think it was me and one other guy that really liked Vista, so I'm even happier with W7.