i'm impressed with it for low and slow. i did two butts last night with it and a full charcoal ring with pecan chunks minion style lasted almost 16 hours and i never had to stir the coals once. with the old style and the 1st grooved style i would have to stir the coals after 8 hours or the ash would start smothering the coals. and i would have to add charcoal after about 12 hours just. from looking in the bottom of my WSM i can tell the ash is much much less. i still prefer lump but i will get more if HD runs the same memorial sale this year.
I fully packed and over loaded the ring a couple weeks ago to do an over night butt cook. It went over 16 hours with doing nothing other than adjusting the vents open a bit at the end.
After the butts were done i stirred the coals a bit to knock off any ash. Then added the rest of the bag on one side.
I did three slabs of BB's all on the same bag of K. The one thing I did notice the next day was the bottom was totally filled with ash. I guess that would be the norm for 20lbs of charcoal. Vince