I have XP SP3 installed both at home, and I have deployed it to our machines at work (about 400), with no problems; except for the aforementioned processor incompatibility. We used to have an Intel-based environment, but we are switching to AMD processors because of the lower cost, and I have started creating separate AMD and Intel images so that we can load SP3 without worry.
SP3 has been in production here for about two months.
I initially had problems with a few machines, but AFAIK only because we loaded an image created on a machine with an Intel processor. The processors we use in our machines are Athlon 64 5200+.