Armor Lock isn't overpowered. You just suck at Reach :)
Reach isn't bad, you're just a BK :)
For my gamertag, look up "Ghoulishtie"
OK! HERE'S THE FULL ANSWER!
ODST comes with 2 discs. The first one containes Halo 3: ODSTs campain, firefight (new game mode), and theater. (along with extras like the Halo: Reach beta)
the 2nd disc is pretty much Halo 3 minus campain. It has all the new maps up to mythic, so its pretty much Halo 3 multiplayer all in one cd. That includes forge, theater, custom, matchmaking, etc.