It'd be nice to have an audio fade slider for when VoIP is active (and maybe even for when in-game characters are talking). I'm enjoying the multiplayer, but it's not really possible to hear or be heard without manually cranking down the game sounds, which leaves you unable to hear them when no one is talking.

Additionally, about halfway through the campaign I ended up turning down music/effects relative to the voice volume so that I could hear some of the indirect speaking more clearly (e.g. when you're sneaking up on some baddies and listening to them talk among themselves.

As an aside, the "It isn't safe!" exchange was one of the most awesome bits of game for me, but I had to turn down the other volumes and turn on subtitles to understand exactly what was being said. I was very happy to see, however, that id put in subtitles. I remember a few QuakeCons ago when John was asked during his post-keynote Q&A why id hadn't included subtitles for the deaf and hard-of-hearing (WRT Doom3, IIRC), and he basically said that it hadn't occurred to them. Always great to see a company that's willing to listen to feedback!