The early collapsible Elmar 90f4 is a bargain. Usually they go for around $150-250. It has a classic look to the negative, quite smooth. It can flare though. What I like about it is the pure esthetics of the mechanical construction. It is heavy, but rock solid! Probably the most "mechanical" of any of the Leica lenses.
Optically it is supposedly the same as the "rigid" Elmar 90f4, but I have ale ways felt that the assembly of the collapsible took it one step closer to "blue-print" status and it an edge.
I tried the new collapsible Elmar and it is very sharp, but it lacks "soul"! If they had made the macro adapter compatible with the old one, or even with Tele-Elmarits I would have gotten it in a flash.