Two things to take into consideration:
1) At the moment, the drivers for this card are ass. Many people have been having problems with the 8.6 drivers and the 4850, with many reporting a hit in power from the various 3870s on the market. That being said, this is a problem with all new graphics cards, and ATi cards in particular.
2) At $200, it will face heavy competition from the prior 3870 (which can be had for half that and isn't any slower in many cases at the moment, and Crossfire gaining acceptance doesn't help matters), the 3870 X2 (which is a tad more expensive and a bit less reliable, but a hell of a lot faster) and the nVidia 8800GTS 512 (which is still somewhat of a gold standard now that it has hit the $150 range) and the 9800GTX (which kinda blows, but is still nearly as quick for a little less money).
Ignoring those two points, now we see what the GTX 260 can do. The 4850 has been shown to be roughly comparable to the 9800GTX (which in turn was quite a bit slower than the 8800GTX), its current nVidia price competitor, though it manhandles the nVidia when AA is turned on at high resolutions. And that is despite 8.6 driver suckage (I imagine total elimination of its current price competitors once the drivers get sorted properly, especially if ATi pulls out an X2 version). The GTX 260 should be comparable to the HD 4870 more than anything, but we will see.
Michael: Jodie, how's my schedule look for today? Jodie: You've got a conference and dinner party at the Japanese Embassy regarding wildlife protection. Michael: Oh, yeah...sorry, but I'll have to cancel that. I'm heading out to save America!
Perhaps. Though the problem isn't as widespread as, say, the 8800GTX to the 9800GTX, the fact that introductory ATi drivers are traditionally poor makes me suspect that the card is much better than the computer is allowing.
Michael: Jodie, how's my schedule look for today? Jodie: You've got a conference and dinner party at the Japanese Embassy regarding wildlife protection. Michael: Oh, yeah...sorry, but I'll have to cancel that. I'm heading out to save America!
The main limiting factor that the two cards will face is ATi's resistance to advancing past what the Radeon 9700 offered in terms of memory bus. With as many shader processors and as ridiculously high memory clocks as the 4800 series has, its 256 bit memory bus (albeit broken up into very small chunks) may bottleneck it. That being said, it should be able to hold its own against the GTX 2x0 series if ATi plays the pricing right (which they currently are). The 4870 will never touch the GTX 280, it seems, but it may give the GTX 260 a strong run for the money. And with ATi's baffling ability to do twin-card solutions better on a hardware level than nVidia has ever been able to (being mainly let down on the software side of things), they may yet pull a win out of the closet if they pair a couple of 4850s (or underclocked 4870s) and sell them as one for the $400 price range.
It really depends on what nVidia does, and if their last go around against serious ATi competition (the disastrous FX series) is any indication of what will happen this time, there may be a grand fight for supremacy.
Michael: Jodie, how's my schedule look for today? Jodie: You've got a conference and dinner party at the Japanese Embassy regarding wildlife protection. Michael: Oh, yeah...sorry, but I'll have to cancel that. I'm heading out to save America!