So... basically, it's an expansion pack like Brood War or Team Arena? Same game, nearly compatible for mods, incompatible for multiplayer, splits the community between the people who bought it and the people who didn't, and you can only hope everyone does buy it?
... except that they've skipped the expansion pack stage and gone straight to the "gold edition" bundle of game+expansion, at the original game price, thus saying "sucker, you should've waited for UT2004" to everyone who bought UT2003 when it came out.
Yeah, *that*'ll work well.