It kind of reminds me of when I worked in construction and we switched from regular hammers to gas powered nail guns. Sure the things weighed about 5 lbs more, cost more for the gas and nail strips, stunk to high heaven and tried to pull your pants down when hooked on your belt. But man we sure could drive a bunch more nails in the same amount of time.
Not a good comparison, or maybe it is. Hammered nails have about 30% more more holding strength than shot nails in typical pine framing lumber. Of course you can shoot 6 nails in the time you can drive one.
Well in either case I'm glad I'm editing audio / video in Vegas rather than driving nails.
To make my first contribution in this thread (slightly) more on topic, I have installed SP3 on one of my old clunker machines that still uses XP. (P3-866)
Seems to run about the same. Definitely did not have a negative effect.