I've used the beta myself, and personally, I kinda like the blue better. But this does look pretty sweet. As far as the start menu goes, the new one is an atrocity. Its actually slower to come up, and aside from the most used programs, I dont see whats so special about it. Thats what the desktop is for. Although MS seems to think the desktop should be clear and the start menu should hold all the programs. Better yet, some idiot decided to put the all programs list BELOW the most used program icons. You zip over the all programs as you reach for the most used, and next thing you know, youve got your entire list of programs blocking the most used ones that youre trying to get to. Kinda defeats the purpose doesnt it?
As far as compatibility and stability goes, I havent had a single problem yet, and its a beta. The thing is though, unless programs specify it, they wont use the new look of the buttons. The menu bars and frame will be updated, but the buttons wont. It'll be a little time before all the programs are specified to do so, but its like two lines of code, basically just a permission. Probably why all the apps work well, and theres no formatting problems.