What OS would you use?

I'm in the process of compiling a list of components for a new computer which I'll build myself (with some help). Now that Windows 7 is officially released - or about to be - what OS would you use? Vista Home Premium-64 is what I'd planned on using, but I hate to buy it when Windows 7 is the new standard. Until Windows 7 SP1 is released I have some hesitantcy to use it due to potential bugs. I don't think you can get an upgrade coupon when purchasing the OS for yourself which makes buying 2 OS's out of the question. Thoughts?