yeah, interesting point about good techno not having vocals. I don't particularly agree, but I'll qualify this - a song like Silence / Delerium ( DJ Tiesto mixing sarah mclachlan ) is about the best vocals & techo gets. As long as the vocals flow with the beats, and don't steer the song (like a typical top 40 piece of crap song does), then all the sound flows together. and that is what makes a good tune.
incidentally a good rule of thumb is that if there are more than like 10 different words vocalized then the vocals are taking over. or at least that's what I tend to think, when thinking...