According to this post on the official Atari forums, a member asked whether or not it was known if UT2007 would release on the PC first and whether or not the game would be a launch title for the PS3. Well both questions were answered, along with a question about a demo:
"PC first. Were not scheduled to be a ps3 launch title, not certain
where those news sites are getting that from. There will be a
pre-release demo (on the PC at least)."
So there you have it, UT2007 will come out for the PC first, and will not be a launch title for the PS3. There will also be an upcoming demo for the game
Now you can all breath a sigh of relief