Like I've said before, I only had issues with 3 or 4 pallets having ROCKS disguised as coal. Those pallets were mixed in a 14 pallet load I got in '11. It was a test of my patience, I can tell you that - I think I set blood pressure records the last 2 seasons!
My ol' man had bought coal around the same time from the same place, and he too had his grates jam open several times before we ran through that crappy batch. Before that, it was fantastic - that's why I dropped the coin on the truckload. After those 4 crap pallets here, everything was good. The ash wasn't as fine/powdery as before, and was a bit darker grey in color, but still threw heat out and gave easy 24 hour burns.
So far this season, I've burned over 4.1 tons of bagged rice. Other than some bags having a gallon of water in them, and just a few pieces of nut & stove coal mixed into a few bags in one pallet, it's been great too. Using less coal during the coldest winter in years - I can't bitch.