Have a IIIc and love it, but you really have to be in the mood to shoot it (I don't choose it very often, but every once in a while when I really want to focus, or want to restore my appreciation in how far even classic mechanical cameras have advanced).
The RF is great if you get a good one. I got mine CLA'd by Youxin Ye shortly after I got it, and he installed a new Japanese-sourced beamsplitter. The contrast increase makes it super quick/easy to focus (since it's 1.5x). The shutter is quiet, but not as quiet as my M4-P. The need to trim the film leader is really annoying (one of the reasons I seldom take it out), and the relatively low-tech viewfinder is 50mm lens only with no framelines.
If you find one in good condition, or even if you get a user and have it CLA'd they're tremendously fun cameras if you simply accept that everything about using it will take roughly 1.5x as long as with an M camera (focus, loading, framing, rewinding, etc). Sometimes that's just what you need, though.
They make great platforms for pocketable cameras with a collapsible 50 (either Elmar 3.5 or Russian copies, which are just as good optically if you find a good copy (though that's the hard part)). Another way to use them is for wide-angle LTM lenses (the CV ones are excellent and not so expensive) and hyperfocaling (negates need for slow focusing), if you put an accessory viewfinder on it (negates any problems with tiny VF window framing).