I have an air chisel gun... I think one of the keys is to have a high strength alloy chisels, as the ones that usually come with the cheap hammers are too soft and deform too much, IMHO. Also recommend at least on longer chisel so you can get some leverage.
Don't forget really good hearing protection, beer for your neighbors & lots of patience.
Some rivets come right out, some not so much. A few are just friggin hard to reach.
I found that drilling into the rivets a bit seemed to help with the stubborn ones. I think it would help if you could heat the rivets with an induction tool but that theory is untested.
I have to say the cheaper ones can be nice - until you try a better one and realize the difference.
I had a lesser one until I had to pop rivets out to replace ball joints on the Yukon and it might as well have just been making noise (which it was doing a lot of). The 118 got them right out.