Mostly positive, since I don't play online much these days and have used voice chat maybe four times in my entire life. It's always nice to find a player who's willing to coordinate and think more strategically than just smell their own farts all day. Mostly this has happened in co-op games like Diablo and Borderlands.
But I have to wonder if 85% of the world's population is clinically retarded judging by how often I've ended up on teams with 6 snipers and maybe 1 or 2 players trying to actually do something on TF2.