The PC modding community for The Elder Scrolls is very large, thanks to the flexible, easy to use Construction Kit that comes with the game. (I'm aware Dragonage and others also have similar things, but not as large as TES) There are tens-of-thousands of Oblivion(TES game before Skyrim) mods out there, many of which make the game more enjoyable. From little things like UI tweaks, bugfixs, to even adding new landmasses. Another extra is that certain console commands or unofficial patches give the PC version an availability to bug fixes which the 360/PS3 version lacks.
But of course Oblivion has been out for a number of years now. Skyrim probably won't have too many mods until a few months after release. But if you're uninterested in mods the above probably isn't very interesting to you.
The graphics will no doubt be better on the PC. A 955 & 6850 should run this wonderfully, the Xbox 360 has weaker hardware than that. As for controls, that's up for debate^. I personally prefer PC controls for first-person games. I find that mouse and keyboard are a little more precise than using a controller. But I like to do silly things like rearrange the books on a shelf or stack hourglasses on-top of each other, so for you it could be different.
Have you played Fallout 3? That game is also from Bethesda Studios, so that should give you an example of how the controls handle.