Like Hlvr said, it's all about optimization. I ran Crysis 2 on gamer settings pretty much flawless, and my PC is from early 2008. Unfortunately, have to agree with Hlvr that Bethesda history is disappointing concerning this. Judging by the screenshots and video footages we've seen so far Skyrim will require twice the power of oblivion PC to be ran properly. That's my guess at least.
They are running on the same Xbox, and they are bragging about how much they were able to squeeze out of the system, so maybe it's better this time. Wouldn't bet on it though.
I'm saving money since the release date was announced (actually, I'm always saving money for a new computer), and I plan to buy a new one by the end of October.