I have found that I a lot of the time play WoW by ear. I am not always conscious of this, but I notice immediately if I for some reason can't have the sound on. If a party member is behind me, I notice the attack by the sound. If somebody tries to reach me, I hear the little ding announcing their whisper. If there is a rogue in the vicinity, I listen for the sound of the rogue fading in and out of stealth.
Right now I am fishing on the other computer. I don't need to watch it, because when the bobber jumps, I also get a sound warning - a splash. so far I have leveled my fishing ten points - five just during this post.