SP3 does trash the occassional machine though. I have a nice Thinkpad x60s which won't boot after SP3. Tried it twice so far. First time I lost the whole HD. 2nd time, a year later, I had an image backup so it was OK.
Just something to watch out for... this was a major issue at the time ans M$ set up a special hotline for affected users. I spent some hours on it myself, on the first occassion.
However other machines I have built (many) updated to SP3 OK.