I know two people with a Z1 and have driven one. It's not that far removed a driving experience from your E30 325i convertible to be honest for the majority of the time. They are not much or feel any quicker. However it's the drama and cool factor from the doors, exterior to the funky interior that makes it stand out. Would I have one? Yes absolutely if I could afford one. Values seem to have started climbing recently having sat quite stable for years.
If only I had bought the Irish car that sat in Rathmines for years. And the removable body panels idea, that they can be swapped quickly is bull. One owner I know has tried it. I have a brochure for one too