I can go crazy sometimes with City of Heroes, but I gave myself such bad carpal tunnel syndrome with it that I really had to cut my playtime. I substituted Silent Hunter III and Dangerous Waters for it because there's no typeing involved and not a LOT of mousing around and clicking.
Between that and my music making, I spend a LOT of time in this computer/music room. My wife has never considered divorcing me over all this though *knocks wood*