I have the Craftsman C3 cordless impact gun (along with the C3 air compressor which is GREAT for the track and the drill which is a decent drill, and I also have the little C3 shop vac.). The imapct gun works great at the track. I've done hundreds of wheel changes with it.
However, I REALLY really really recommend getting the High Capacity XCP lithium battery for it. ( http://www.sears.com/shc/s/p_10153_12605_00935702000P
) It's SO FAR superior to the either the Ni-Cad or standard lithium, it's not even funny.
The ni-cad battery and the standard lithium can ALMOST do two full sets of 4 tire changes on one charge. This includes breaking and removing bolts and putting them back on lightly for a final hand torque. Sometimes I used to have to break one or two bolts with a breaker bar at the end of the day if I didn't bring a second battery with me.
The XCP battery-----hehe----that thing goes FOREVER----and ever and ever and ever. You could probably do more than 10 full sets of wheel changes on a single charge with that battery. The reason I can't tell you for sure is because it never runs out. I use it at the track to switch to my track wheels in the morning. Then I'll rotate my wheels. Then someone else will borrow it. Then I move the battery to the air compressor and use it to pump air. Then I rotate again. Then someone else borrows it. Then I switch back to street wheels. Then once I get home, I pull the wheels to switch brake pads......and the thing just keeps going and going.....the only bummer is the battery itself is $85 online. Oh, and the XCP battery gives the tool more torque too because it puts out more power.
But as far as the impact gun itself, it's fine for track use at these torque levels (88 ft lbs). It also breaks the bolts on our X5 which are at 102 ft lbs.