David, I think that you can get tight temperature control if you take a few minutes to "tune" the pellet delivery after the food is inside. I'll see if I can find a graph from stoker that I use to monitor my PG500, it's used as a remote-reading thermometer and grapher, not a controller.
Okay, I cooked salisbury steak at 350° in my PG500 last night. Here's the temperature graph–
It was rolling along at ± a couple of degrees variance until I peeked in a little after 6:25. Then, when I again opened the door to put vegetables in, the temperature was upset and I never gave it a chance to recover because I opened the doors a third time.
I'm confident that it would have continued with a flat temperature line, like the first 10 or 12 minutes, if I'd not kept opening the doors. That's pretty tight temperature control for a timing-based controller.