I actually just watched Minnesota Clay this afternoon for the first time and, for the most part, enjoyed it.
The first copy that I had was a cheap rip from, it appears, television and extremely grainy/clipped and I decided that there was no way I was going to watch it.
I agree with those that prefer the downbeat ending to the happy one. The happy ending doesn't even make sense in the grand scheme of the film, which is set up from the very beginning (be careful, Clay, or your eyesight is gone for good). I suppose the "twist" that Clay wasn't really going blind after all was just too much to pass up for Corbucci and Bolzoni.
The funniest part (and I don't know if this happened with other copies) is that the English dubbing cuts off (and goes to Italian) as Clay appears to be dying, with his daughter hovering over him, screaming for help. It's almost as if this copy is warning the viewer to beware that something out of character is about to happen.
All in all, though, I liked what I saw.