I have a ir 231, and is it pretty good. I am an industrial mechanic and bought an ir 2135 a few years ago for about twice the cost of the 231, but it is awesome. I keep that one at work since it gets used more there. I personally don't think it really comes down to how much you use it to justify buying a good gun though. If I were to only use an impact 3 times a year- I would want it to do what is asked of it those three times. My dad always had cheap impact guns and they wouldn't break anything loose, I would have to break it loose with a breaker bar then use the impact and I didn't see a lot of time savings so I was kind of turned-off to impacts. Well I bought a better one (the 231) when I was older for the heck of it and what a difference it made, made me like impacts again. When I bought the 2135... holy cow! I love impacts now. If the need arises, I may buy a snap-on gun next, but the specs don't seem much better than the 2135 to justify twice the cost. I just don't see myself ever buying a cheap impact, I would rather do the work by hand since it takes nearly as long, unless the cheap ones have gotten better since ~mid nineties.
Tried a dewalt corded electric at my old job (we also had a b&d that was identical) and it was ok, I could see the convenience of electric, but it did not do what a good pneumatic would do. They also had a ir 2141 3/4 pneumatic that was really good, maybe someday I will buy one of those as well.
. Okay, too much caffeine.