Having the DVD over the 6 CD's is awesome. As is the extra characters.
Oh and the included mods are a blast though currently a little out of date (RO needs a update badly but is still awesome).
You may have noticed that I am reviewing this compared to the basic UT CD version and that is correct. Is it worth it for everyone? Depends if you mind swaping the CD's in and out while installing. I for one hate that with a passion. So for me this was well worth it and I have spent far too much time with it.
The Multiplayer is of course awesome and the few extra maps are really nice. My favorite is to play online with Low Gravity and Matrix Moves on a site that has an MP5 and the Zark sniper rifle on Onslaught maps. Sure I have played through the game on different levels close to 20 times but I have spent probably well over 100 hours playing this online on different names and such. As for how much time I have spent offline? Who knows. I think I have still played more offline then I did online but one never knows...
The bottom line? If you don't have UT 2004 yet you should get it as it is the best pure shooter out there. And the DVD version should definitly be on the top of your list. And it's usually a very reasonable price these days too as it's not exacly the latest game to the market.