I actually have a DeWalt corded impact wrench. Good for ~300+ lb-ft of torque, IIRC.
http://www.dewalt.com/us/products/to...?categoryID=50
Absolutely no sweat getting off lug nuts.
It's nice that you don't need to fire up the air compressor to run it. . . just plug it into the wall and go. Only thing is that it's a bit noisy. . . seems noisier to me than an air impact gun for some reason. Besides the hammering action you also have the electric motor making noise.
And it's bulkey and heavy vs. an air impact wrench. Definitely not something you'll be using in tight quarters.
That said, i usually just grab my cross-type lug wrench to spin off my lug nuts. Partly because I'd just assume not make such a racket and the lug wrench isn't that much slower.