@Cronox - you already got the general consensus. One thing people haven't mentioned is that just
using mods takes time. After Skyrim was announced I went and replayed Morrowind & Oblivion on PC. I used > 300 mods (not even counting the texture and mesh mods) for each. Having been through it before, I knew what to expect, and spent more than a week on each game, prepping for a stable, usable mod setup. If you use a few mods, you don't have to worry about it. When you start getting to 50 mods or so (not counting textures/meshes/animations), you have to put work into it. When I had Oblivion setup finally, it was far more stable, performant and bug-free than vanilla ever was, but it took patience and research.
Also, while a decent PC will blow away a console for performance--even on ultra settings--certain types of mods will eat all of that extra power and still want more. So that's more work, still. Even simple things like textures turn into a headache. I've got > 3GB of textures already, and I'm at the limit of what my GTX570 can handle (in some cells). Now I wish I'd shopped around for a card that offered greater than normal VRAM. So I have to go back and reasses my texture setup whenever I update or add new textures, otherwise my performance might suffer. Yeah, I could just remove some, but that would be wrong.

So you'll get a ton of new content, thousands of bug fixes (eventually), potentially better performance, much better visuals, and have the option to personalize the game more than you'd imagine. The downsides are a huge step up in cost, and a lot more of your time. But once you get svcked in, you won't mind.