SP1 fixed much of what was wrong with Vista and I support numerous folks who use it, including a handful who run 64-bit Vista on $10000+ workstations. It's a perfectly fine operating system that's not giving us any problems with stability or performance.

I never did see it as a big enough improvement over XP to recommend spending extra for it, but if someone orders a computer with Vista, I no longer automatically wipe it and install XP.