A detailed review from Game Spot (spoiler safe)

Gamespot gave it 9.4. Summing up, they say that it's a superb game but only subtley different from Halo: Combat Evolved. There are new enemies, vehicles and weapons and a few minor tweaks in the gameplay. Overall everything seems to play out on a slightly larger scale.

On the minus side, the single player campaign is short, has a weak storyline and apparently ends quite abruptly. The repetitive level design from its predecessor also makes a return.

Several of my friends own XBOXs and I'm looking forward to seeing this and maybe teaming up in 2 player co-op mode.