I have a Porter-Cable 1/2 inch impact wrench, which I run from a Porter-Cable 5 gallon side-stack 5.3 CFM portable compressor-- which most people would say is undersized for the impact wrench.
I find that as long as I'm willing to pause when I hear the compressor kick on, it runs the wrench just fine. For non-pro use, how often do you need to sit there and use an impact wrench without interruption, anyway? If something comes on or off, it does it in a second or less, and then there's usually some time before you have the next one ready anyways.
As to the detractors of impact wrenches, I, too detest situations where people over-use them to do things like install lug nuts. Properly used, though, you can regulate the torque. And for taking apart corroded items, I find that one can often get things apart-- more readily AND with less net damage-- than with a breaker bar; the many small impulses of torque seem to work corroded threads apart more easily, and with less damage, than one steady application of torque which might just twist something into pieces. Like any tool, it's all about using it properly for the proper applications.
