The Dretch coming from behind thing is also 'cheating', although is far less useful than peeking around corners.
On the subject of a useable 3rd-person camera, did you people already forget the horror that was unleashed upon us gamers once 3d platform games became popular after the release of Mario64? Remember how just about each and every one of those games sported a horrible, uncontrollable and generally annoying 3rd-person camera? It's a rather tough job to code a good, useable 3rd-person camera. The only ones I know running on id Software code is what Raven came up with for Heretic2 and what Ritual did with their Quake3-based UberTools (FAKK2, Alice).