Apparently the "new" 260 is not as much crap as had been thought.

http://techreport.com/articles.x/15651

Despite the fact that these are tremendously complex chips with hundreds of millions of transistors, AMD and Nvidia have achieved a remarkable amount of parity in their GPUs. In terms of image quality, overall features, performance, and even price, the Radeon HD 4870 1GB and the GeForce GTX 260 "Reloaded" are practically interchangeable. That fact represents something of a comeback for Nvidia, since the older GTX 260 cost more than the 4870 and didn't perform quite as well. If anything, the GTX 260 Reloaded was a smidgen faster than the 4870 1GB overall in our test suite.

The GTX 260 is based on a much larger chip with a wider path to memory, which almost certainly means it costs more to make than the 4870, but as a consumer, you'd never know it when using the two products, so I'm not sure it matters much for our purposes. Even the GTX 260's power consumption is lower than the 4870's, and its noise levels are comparable.
This is quite the reversal from techreport compared to their earlier R770 vs GT200 reviews. If the new 260 is capable of this, then the new 55nm versions may actually be worth while.