I've burned nothing but Kimmel's for the last 4 seasons. This will be my first year with Blashcak, because they jacked the price up a bit too much at my usual supplier. The first season, I found more crap in those bags than I thought possible. Once found a wad of mud with a boulder in the center, slightly bigger than a softball .... I found wire, countless chunks of wood & roots in every different size, shape & form. Some of them blend in pretty good with that coating of coal powder!
The last couple years it's been just chunks of wood. At least wood burns - that mudball wasn't very flammmable...
Just jammed my grates open requiring a cleanout.
I noticed varying sizes in the nut coal. It was more like pea than nut - or a mixture of the two last year. LOTS of fines - more than in previous years. Last year it seemed slower burning with less heat than in the past.