Tom, as a friend, I have to be honest, I'm not feeling the start menu. The four colors don't look good. If you had green on the bottom left and yellow on the bottom right, then the search and the log off buttons would match up and have a much cleaner look.
I do like the idea, it's just the execution that's off to me. The thick black borders, I'm on the fence on that one.
I hope the idea, for the previews, is to get feedback. If not, then I'll shut up.