I kinda have this in Borderlands as I play as the soldier. I have a class mod that gives all my team regenerating ammo, plus shields that regenerate health slowely and I think my friend also has a class mod that regenerates health etc
For a game like this where we essentially just "whore" for XP and more loot I don't mind it so much but for other games that have a more indepth story I do prefer picking ammo up (or in ME1's case, overheating guns which I prefer a lot more to ME2's picking ammo clips up). Having said that, half the guns you can pick up in Borderlands are pants anyway and the only way to do any real damage to some of the enemies is to just endlessly spam them in the face, so regenerating ammo is useful in that respect lol