I don't suggest doing the "buy Vista now and get a free upgrade to 7" thing. I did that when Vista came out, so I own a copy of XP Pro and an "Upgrade" version of Vista Business.

Upgrade versions are terrible, in my opinion. Should you need to reinstall the OS, you need to go right back to install the OLD version first (in my case, I'd need to install Windows XP Pro) and then upgrade that existing install to the new version (in my case, Vista Business). It's a major major PITA. Like 2+ hours extra for a simple install.

The other drawback is that you're carrying stuff over from an old install, even if it's a fresh install it's still got stuff that either doesn't work in the new version or is in there for legacy support which you don't need on the new OS. Extra crap just bloats things up. I never felt comfortable with my Vista installs knowing that they always had some remnants from XP in them.

Wait for the full 7 release in October (unless you're lucky like me right now and have an MSDN subscription through work, hurray!). Install the full version and pretend you never heard of Vista, you'll be happier

Good luck!