I am behind in posting about this. I have been a fan of the Halo games ever since I got back into gaming. Halo is one of those games that has advanced the entire field of gaming and the expectations heaped onto other games.
I have never been a fan of any Halo multiplayer. Too many screaming eight year olds and it takes way too much ammo to put someone down.
With all of that being said ODST is worth atleast the rental. The story mode is top notch. It also has a co-op mode called firefight where you and up to three of your buddies play online against the hoard clearing wave after wave.
If that isn't enough to convince you, this might. Most of the voice work was done by Nathan Fillion, Adam Baldwin, and Alan Tudyk. Fans of scifi will know these folks better as the main male characters in the defunct series "Firefly". There are a number of Firefly references in their dialog. Some pretty funny stuff.