Infinite Ammo design is bad for many reasons
1) It takes away the tension of running out of ammo
2) It diludes reasons for strategic thinking as you can just go on shooting untill everything is dead
3) Only option to counter overpowering the weapons due to infinite ammo is make them have very low damage. I've seen this in some games and it's not fun, practically making such guns toys
4) Not even Invisible War had infinite ammo and remember how bad its uniammo mechanics were compared to Deus Ex's.
I see no single positive thing in infinite ammo design. Letting you loot corpses, buy ammo (like other equipment) etc. is dead easy thing to include. As there's nothing to gain from this design - in fact I believe it'll weaken experience just like other times when I've encountered it - I think it would be better for quality of game change this design.
Blizzard has practically halted their project sand started design again from the scratch sometimes. This infinite ammo design is small part of overall mechanics and shouldn't be big thing to revamp at all.
So please Obsidian, considerate this. I don't typically care enough to go and start petitions etc. when it comes to games and such but this caught even my ire with its stupidity
Xard