Although an Apple fan boy, I still have a Window Laptop for doing .NET dev work on. The machine is new and came with Vista pre-installed. I have MSDN and considered re-installing XP, but thought I would give Vista a chance seeing as I paid for it!
Initial experience was ok, but I felt the internet was a little slow. This was bourne out by testing - my Macbook Pro, and XP via boot camp was around 7000kb/s down, Vista came in at around 4800kb/s. All on the same internet connection. I did a little research and discovered other people were having issues too. I tried all the resolutions to no avail.
I was about to give up on Vista, when I noticed RC1 of SP1 (say that 10 times fast) was available to download. So I did - nothing to lose.
Installation was fairly painless, it comes in via Windows Update. The whole process took about 25-40 mins, rebooted a few times and fairly painless.
The whole OS feels snappier, and I rebenched the internet connection and it was up to 8000kb/s. Ok hardly scientific but the results speak for themselves.
Hopefully, SP1 for Vista has ironed out the many issues that people were having. It seems to have for me so far.