I've successfully installed SP1 on a number of machines, no glitches.
I support two machines with ATI Radeon 4200 cards, however, that have experienced some serious resolution difficulties. Both are 32-bit Windows7 Pro, Intel Duo-Core. The issues are with WVGA screen sizing when running on larger (not 'optimal') screens (for vision difficulties).
Since part of the reason you are doing this is video, you might check out forum comments and MS Technet relative to your specific video card before doing this upgrade. I'm sure there will be drivers to fix any issues at some point ... but limping through a few weeks waiting for them to come is annoying if it can be avoided.