One of my co-workers installed Windows 8 on his laptop with no problems (it was running Windows 7). I'd guess that your problem isn't that common or else it would have been caught by beta testing. I recall that you have a custom rig.
I'm planning on upgrading too with the special deal. Vista is just incredibly slow at startup, shutdown and regular use. Even with a Core i7. My Merom-based iMac starts up, shuts down and generally runs OS things faster than my i7 which is ridiculous. It's a lot better with Windows 7 (I have an identical system in the office running Windows 7) and it should be a lot faster with Windows 8. One thing that I will miss on Windows 8 is Gadgets. Gadgets were abandoned for tiles. If Gadgets work, that would be great. I prefer a small sidebar with calendar, clock, weather, stocks and CPU thread usage over covering the screen with tiles.