Well, there's some truth here on both sides. A few days after the game was released, Mark Reign (sp?) made a semi-lengthy post on the Infogrames site (tech-support section, IIRC) which I found strange for several reasons.
He stated bluntly that Epic had never used--even once--an R300 in the development of the game even though, he said, they'd had a prototype 9700P sent over from ATi "sitting unpacked in a box" for sometime. He then went extremely apologetic for some reason, because some people were reporting "problems" with the 9700P in running the game--problems no one at Epic had as of yet verified at the time Mark made this post. Mark vowed to quickly test and correct any problems they found.
I responded that I'd had zero problems with the game and was very surprised to learn Epic had not used an R300 in the game's development. In other words, had Mark not made this admission I simply would never have guessed it. Game ran great for me ROOB with my 9700P. That's the truth--I saw nothing which would have remotely led me to the conclusion Mark admitted. His apologies were very premature, at least as far as I could see, and I told him so...
I suppose that after he got a production R300 9700P up and running with the game he must have agreed as he had very little more to say on the subject.
I think it speaks it well of ATi's DX driver efforts, as well as Epic's DX code base, when a new product like the 9700P never even used in the development of a game like UT2K3 runs it near flawlessly ROOB (I don't recall any significant problems with it.) In the days that followed I stayed attuned to the forum and thought it extremely interesting that by far the lion's share of the problems reported there concerned nVidia 3D products...! Granted, the general technical skill of most of the people who frequented that forum, as far as I could tell from the comments, left a great deal to be desired and I suspect that many of the problems (regardless of hardware) were matters of basic system configuration. I thought the whole episode was very telling and very interesting.
I agree with those who fail to find anything of substance behind the "The way it's meant to be played" paid promotional which nVidia obviously paid Atari to put there (I substituted an ATi logo a few days after buying the game.) As long as nVidia continues to market "special feature" support without documenting what the features are, a highly skeptical attitude is justified. I've seen nothing in the game to justify such a claim.