You have to have a really good computer to play this game, first off. You want to have a good bit of overhead over their recommended specs in order to really enjoy the game.
The game itself is wonderful. Weapons are well balanced, gameplay is smooth and intuitive. The AI has the "kill or be killed" mentality of UT, so it lacks the polish of...say...Splinter Cell.
My only problem is that it really isn't that long. I beat it after two days of consistent play. And the replay value is absolutely nil. There is currently no deathmatch support.
For a lot of people, the amazing gfx are going to make up for this...but I'm not one of these. I miss the days of Doom2 where it takes MONTHS to beat the game. Or maybe that's because I was so young...
Overall...yeah, it's cool. It's worth playing. But I didn't think it was properly priced for the duration of gameplay.