I have a 3 in 1 machine I bought for aluminum bending and some small sheet metal bending I've been doing for building my hot rod (an AC Cobra) for the floor pans, inner fender liners, trunk pans, and a few other parts. Also use it for projects around the house. I've been pleasantly surprised at it's capabilities with the shear- I've cut up to . 090 aluminum and .060 sheet metal with it with some effort and it has cut clean and straight. I bent some .040 and ,060 aluminum, which is slightly over it's capacity but it seemed to work okay, but needed a bit of extra effort to get good 90 degree bends. Never could get the roller to work to my satisfaction, but I never really tried it with the 22 or 20 guage sheet metal it is designed for, so probably operator error on that one.
Mine is a 30" machine and seems to work okay. Definitely needed a bit of fiddling at first to get it set up right, but the previous owner had used it in a sheet metal shop so it had most of the break in already accomplished. Not sure what manufacturer it is, but I'm pretty sure it is a Harbor Freight unit. Seems pretty well put together but definitely not a production level machine. I think for the most part, these machines if assembled and manufactured properly and you check them for this before purchasing, will be fine as long as you stay within their ratings.
There are ways to work copper and other materials without damage by making inserts to protect the metal while working. Some type of phenolic material should work fine for inserts, or even just a thin piece of UHMW worked through the die to match the shape before bending.
Bob