I am a hard fan of ut, so I know the genre very well. Having said this, I have to give a not excellent rate to this game because of many factors.
On the first hand, the game play.com sold me was a full german heavily censored copy, not the multilanguage copy I was expecting. I don't particularly like blood and other violent things, but I don't like being not informed about the fact I was going to buy a German censored copy.
Anyway the serial is there and can be used with any copy of UT3, if you intend what I mean.
The game presents very well, indeed has a very good graphics, stunning effects and so on.
Actually I played a some matches with Instagib and Warfare mode and was badly impressed by some facts:
1) The UI is pretty console-like, and this isn't good for a PC game, since you can't really configure detail level of the game: there are just two sliders for texture detail and world detail. meh.
2) Servers are almost all empty, I managed to find two or three european servers with 24 or 32 maximum players, but unfortunately lag is always there and very annoying sometimes (I have no issues with ut2k4)
3) Gameplay is fast. Maybe too fast, and this isn't good if you play online, because lagging really kills fun
4) Minor other things, like nodes which lost numbers (so you can't tell your teammates where you need help or which node to attack...)
5) Sound also need some tweaking: for example, the announcer talks talks talks... and you can't hear a manta coming or people firing at you.
The general feeling is like the one I had with ut2003, with a good but imperfect product that still needs to be completely polished.
If you plan to play this in single player, maybe it could be worth it, since the price is kinda nice, but if you want to play this in multiplayer take in serious account that the community is not particularly alive and there still are minor and major things to be fixed.