I was wondering, and I doubt anyone's finished the game yet here, but can you still free-roam and do side missions at the end or does the game just end like Fallout 3?
Edit: I just answered my own question.
"Mercenaries mode is exactly the same as the main story mode except there are no main missions. It is unlocked & available to play in only after you've completed the story & you are able to finish off side-missions, races & collectibles.. & whatnot.. that you weren't able to finish when playing through the story"
Source/Link:
http://forums.eidosgames.com/showthread.php?p=1319876