I've not used their impact wrenches, but do have a couple other air tools thy sell, stuff I only use for light, occasional duty (cutoff tool, air ratchet, brad nailer). They have been fine for the price. Oil frequently.
For impact wrench, I'd actually suggest you hit a pawn shop in an area with lots of blue collar-types and buy a used name brand. My Snap-On cost me under $75 that way, and I've seen plenty of other quality brands under $50.