VISTA Features
I was going to stick with XP-PRO on my desktop based on the opinions of many at techpowerup that VISTA sucks. Fortunately, I was able to buy a new ASUS laptop with Vista installed - my Toshiba laptop, at 720 mhz, was dying. After a steep learning curve, I decided to install VISTA on my desktop. I've found that it loads faster and I now know the tricks to solve all my novice issues encountered with my laptop.
I like VISTA because the OS kernal handles large graphic loads better, the UAC protects against rootkits or hacks, and I like the false security of protected mode IE. The UAC can be less of a hassle with TweakUI and some select group policy changes - still you need the UAC hassle in my opinion to stop rootkits from installing under the admistrator banner. As to compatiblity, you can run a program in XP compatibility mode within the file properties section and/or run in with administrator rights without compromizing system security. I fixed startup program conflicts using Task Scheduler where you can delay startups on some programs that don't like to start side by side, like zonealarm and windows sidebar. (I had a similar problem between zonealarm and speedfan in XP which I fixed with a freeware program called Startup Delayer.)
Regarding VISTA problems in general, every single event issue that has cropped up I have found solutions for through google. In my early XP days google did not exist, so finding such solutions only came through my company IT guys. And I had a huge number of problems with XP SP-1, due to compatiblity errors and user snafus.
As a caveat, both of my machines have 4 gigs of RAM, good dual core CPUs, and excellent hardware and cooling. As has been said before, future OS'es need newer hardware. I loved Win 98, thought XP was a step down but moved on with no regrets - as the newer hardware and software for XP was a huge improvement over Win 98. The same will happen with VISTA and hopefully some linux OS versions.