I run about 6,000.00 worth of software on my machine. The easiest program to install? GIMP, which is a photoshop clone and free.
Go figure.
I run a $100 million dollar financial institution on our machines and they won't / can't be VISTA.

At home, I have 2 Windows XP boxes, 1 Ubuntu Linux box, and 1 Windows Media Center laptop (my wifes). The only thing keeping me from MAC is the cost outlay. You can dual boot VISTA / Mac and have everything you need, or run VM or bootcamp. So many options now on MAC that make it so compelling. I've had several friends switch over the last several months, and a few of them are gamers - which MACs just plain aren't able to do well for a variety of reasons. But boot up Windows on your MAC and your all set.
Only one of our major vendors will qualify that their software will work with VISTA. It's bad enough that everything is browser based these days and IE7 is a cluster @#$#@ of a browser when it comes to pre-set security settings. If the world would just switch to Firefox the net would be such a better place!!
I have my XP Pro box running as a lean machine and I rarely have any problems. There is NOTHING VISTA offers over XP that is compelling enough to switch. Pretty Interface? A security feature that 95% of all users disable? DX10? Yeah.. right.

Oh, and their networking speeds are still lacking behind XP - even with Service Pack 1 from everything I've read.
With XP, 2Gigs of RAM is plenty. With VISTA, just about every article I read states "4GB is the new 2GB", even though VISTA only shows you using 3.x of it in system resources.
I don't know... I just don't see any compelling reason to switch at this time.