"I still think that the GTS will play it at pretty much full quality regardless...DX10 isn't going to add too many incredible features that will cut the frames down by half or anything."
it is contradictory to talk about how great and new and advanced the graphics are then on the other hand say its not adding much. you know that each extra level of detail and the huge environments add to the workload involved in running the game.
even if it is the best programmed game in the world it will still take a beast to run on high res or high settings because the game is so friggin' detailed.
"So why would nvidia make a crappy card that's supposed to be on the new pathway for dx10?"
each time a new dx version is released, traditionally the first series of cards that come out for that version are fairly weak. look at nvidias fx series, their first dx9 cards, those cards struggled heavily in dx9, we haven't even seen the 8800's run in dx10, no benchmarks available, so this is all speculation....this is also a major reason why more people aren't buying the 8800 series yet, they want to wait for 1-2 more generations of dx10 cards being released and be able to see benchmarks so they know their card isn't only dx10, but it runs dx10 games well.
Of course the developer says it runs on high on a 7800gtx, of course their requirements are low, that will help them sell games. A lot of factors in this besides video card, your cpu, your os, ram, what settings and resolution your running at.
I think speculating that an 8800gtx much less a 7800gtx will run the game at 1600x1200 on high is ridiculous at this point.