Vista's user control doesn't have to stay active (you can turn it off, though if you've less experienced users using the computer, I wouldn't recommend it). Though Vista does require some serious system resources, most computers come with more than enough ram to support it, plus ram upgrades are very very cheap (i put 2 gigs of ddr2 into my laptop for $80). I get 3+ hours of battery time with my laptop running vista home premium, and i love it. admittedly there are things that you have to get used to, but the same was true of xp, and xp sp2.
I completely agree with the stability argument above. I've had some program crash, as will happen on computers, but instead of it being catastrophic, vista recovers beautifully, which is more than i can say for xp (especially when and if explorer crashes, where xp would hobble along to the next reboot, vista shrugs it off like nothing happened). I've tried running the UAW trial, which causes my video drivers to crash, and they completely recover without issue (the problem is probably more that I have intel integrated graphics than with vista).
All in all, I think that vista is the better OS. Other PC software and hardware manufacturers are more to blame than MS for performance issues, since problems typically involve driver issues that the manufacturers still haven't worked out.