A pellet sensor will be coming to the 2019 Timberline. I’m guessing this will be a differentiator other than outright build quality, for the timberline lineup. Supposedly very accurate at measuring remaining pellets, not just an optical sensor that sees daylight or something.
I just purchased the new Timberline 850 and does have the new D2 controller and pellet sensor. The thing with the pellet sensor though is that it is mounted over the area where the pellets seem to drop the fastest. In order to get an accurate reading you have to push the pellets around to even them out. Still it isn't completely useless.