Just bought a 110v impact wrench from pepboy's. It is a kawasaki 1/2" impact wrench. It is rated for 220 ft/lbs. This wrench works great! For anyone who has yet to invest in a air tool collection this wrench for $60 is a great deal! Here is a link to the wrench. Here
Before air tools, I had one of these as well. As you say, it works surprisingly well for an inexpensive item. One caution, is that it makes nowhere near the stated torque. I thought it was good for about 120 foot-pounds, which is enough for 99% of routine jobs.
I have the Goodyear 24volt cordless from Pep Boys. Powerful but heavy. The charge lasts a long time. I use it regularly at work to put things together. i would definitely recommend it. $80 i think.