I got the collapsible Elmar in M-mount with my M3 when I bought it as part of a whole bunch of gear; the previous owner said it'd been his favourite lens, and it's certainly had a beating over the years. Scratched front element, very much a user lens... but it still produces lovely shots, and it's really, really compact when collapsed.
Took some test shots (tripod mounted, same film) trying it out against the 90/2.8 "thin" tele-elmarit, and I don't see a whole lot of difference... plus the elmar has visibly warmer colours (which I quite like).