I grabbed Vista Ultimate when it was released. I'm running a custom built liquid computer at home and the nice aero glass theme etc and some of the flashy stuff is quite nice running on it. Flex was a non issue to install and get running.
CF MX7 wasn't exactly strait forward though as you need to change a few things to get it to work properly on IIS7. I spent a while browsing trying different things to get it to work properly and I wish I kept a list of everything I had to do to get it to run properly because there wasn't a single lone fix that worked I had to combine them all together. Vista has its own set of issues like the voice recognition vulnerability where audio played over the speakers can be picked up by the voice recognition executing voice commands form the audio file. This is and isn't a vulnerability but every where I see it brought up it is a vulnerability and not a feature unless it is a message form MS. Side Note: For a laptop stick with XP as Vista eats more ram then XP did just like what ever comes after Vista will eat even more.