After using my 4790k for a few days, so far it idles at around 25°c (on H100i), playing Watchdogs over hr later, it was sitting at 65°c, and that is running at 4.6GHz, I've managed to get stable 4.85GHz without too much messing about, and could of got more out of it, but didn't have the time to sit there and do it.
So in my experience so far, I can't see any reason in which you would need to delid it unless you are going complete hardcore overclock.