Yeah, one serious problem was on HP's AMD based systems. SP3 would overrun the AMD CPU drivers with Intel's or something similar, making boot-up impossible. Personally I've been very pleased with SP3, no problems whatsoever. Tho, not much difference either, minor performance and stability improvements. But because I made dual-boot, I had nothing to lose but time and one CD-R. When I found it to run smoothly, I was ready to make the update on my main-install. Your mileage may vary ;)