I bought the 1600 despite the warnings due to the price being right. I hoped I would get lucky and it would have the updated control programming. I was wrong. It gets up to 300 just fine but is slow as molasses after that. I haven't had the patience to let it get past 450. To go from 300 to 400 it takes an hour then another 30-40 min to hit 430 ish. 452 is the highest I have seen it get. I have 10 cooks on it and have seen no noticable improvement. The outside temps down here have been from 85-92 so being too cold out is not the problem. My replacement controller is on back order for a 2-4 weeks. The tech told me to turn the grill to high every time I start it until the new controller comes in. He said that will help it learn. We shall see.
On the plus side, all the food I have cooked has come out great.