I was all about getting a 260 but then i read this:
Radeon HD 4870: Better Than GTX 260! : Introduction - Tom's Hardware
I know now that you can get a 260 for the same or even cheaper than a 4870 but it appears that the 4870 seems to be a better card, out performing the 260 by 6%. Sorry you might be an nvidia guy, deeming the above a complete waste but this card is a contender.
I get a kick out of this, the hd4870 beat out the 280 here, and the price gap is what like 150-200 bucks?
P.S.: hmm in retrospect this post didn't help you decide between a 260 or a 280 at all....sorry.