I find that most Speech recognition software doesn't work for me unless I put on an american accent.
I once took a technical support call from a very drunken sounding Scottishman with the thickest accent i'd ever heard who was complaining that ViaVoice didn't work for him. I was suprised the keyboard understood him to be honest...
However I do think that speach relay is under-used in multiplayer games. An MMO with speach relay would be something else, if only...