I agree with Ancient Dragon above me completely.
I also have a dual boot set up on this very machine, and it works well for me. XP for the past, Vista for the future (and most of now).
Now, I have my system specs in my profile. If you check it out, you see that my computer is more than adequate to run vista without any hitches. But most people don't want to buy new hardware and updated software, so they turn around and complain when they try to run vista on a machine that can barely handle XP.
What seems to work best is 2 GB of RAM, at least a 2.0 GHz dual core processor, and any video card with about 256 MB dedicated memory, conservatively. But the more, the better!
For me, Vista works great. It looks great, runs seamlessly, and the user interface (while it took some time to get used to) is more intuitive (for me). My opinion is that Vista is a big step above XP, and it is the best Windows OS to date. *IF* you have the hardware.
As for compatibility issues... Thats just something people need to suck up. If its that much of a problem, you can set up a dual boot, or a virtual machine to run XP at the same time. I actually have both.
Finally, vista is the future. Its not going do die out like ME. So we had all better get used to it !
All the best,
--The Comodore