I used this last year until they stopped carrying it (they only sold it during the spring last year).
It sparks a lot while lighting up, but I like it. I love it for grilling. It sparks like crazy in the chimney, and for about 10 to 20 minutes after I dump the coals in the kettle, but after that it is fine. The flavor is great, you do not need to add other flavoring woods, and pairs with beef beautifully.
Some of the pieces are crazy huge, and you may need to either chop them down or find other creative ways to use it.
Oddly enough, when have used it in my WSM's (I have only cooked Brisket with it), it sparks a lot when dumping the lit coals on, but not during the whole cook. If I have the cover off for too long though, then it does start sparking, but that settles back down again shortly after putting the lid back on.
I started seeing it in Sam's again recently and pick up a bag or two each time I go in to stock up. I liked this stuff better than the Frontier lump. I also use the Frontier lump, but what I dislike about it is the amount of fine particles that are unusable. It also lacks the flavor that the Mesquite stuff has.