When you were at 131* after 3 hours, I was afraid that you would not clear the danger zone. I'm glad your pit temp got up to 215*. I would like to have seen it more in the 250* range. IMO, you should get the pit up to temp before putting your meat in.
You also mentioned a good smoke and the pic of your cooker shows a rather heavy white smoke. Again, IMO, the smoke should be a lot clearer and not so heavy. Good bark and color is a product of good smoke, but your butt shows a pretty heavy black finish in the complete view and the sliced view.
Try to get your cooker to temp before loading and try to keep your fire hotter with more complete combustion. Good air flow, both in and out, is the proper solution for this.
Good luck and keep on smoking, Joe.