You can't revive when crouching behind an object, you have to stand a little bit behind them.
Now that's balls, right there! You can't crouch beside an injured pal and patch him up? You gotta stand there with your meaty skull in full view!?!? Not happy with that at all.
I'd be on for some multiplayer action, if my connection can handle it. People seem to be finishing this game rather quickly. Maybe multiplayer is where it's really at in this game, though I seem to remember reading that for a long time the creators were against even adding a multiplayer element.