So there is actually decent driver support for Windows 7 64 bit? I wanted to go 64 bit with vista, but the driver support just wasn't there yet.
When Vista first shipped, there was indeed a shortage of 64-bit drivers, but that was 3 years ago. In that time every manufacturer started shipping proper drivers. So unless you've got some really old piece of equipment there shouldn't be a problem. Especially if you're building a new machine, there's absolutely nothing to worry about.