Well, hosted a game today with v3, and noticed a major bug.
We felt on the default difficulty of "Evil" wasn't good enough, so we set it to "Nightmare". It was insane for 5 minutes, him killing a bunch of people in a short amount of time, but then he just stopped appearing a lot. Every 5 minutes or so he'd appear but not really make an attempt to kill us.
That's the only noticeable bug I really found that hasn't been mentioned yet.
(What's the Anti-Renderman Light anyway?)