This was my first Retina: the IIIc. That's a small "c" -- by the way. And it turned out to be a great choice.
It's easy to see why these were so popular in the mid-1950s. They weren't built to take on Leica. None of the Retinas were. What Kodak A.G. offered was a folding camera with a sharp lens at a reasonable cost -- a camera for the masses. That's the Kodak way, and when it came to the Retina, it was a winning combination.
It features a dual-range selenium-cell meter that is extremely accurate and responsive. Open the flap when the light dims and leave it closed when taking a meter reading in bright light.
The Synchro-Compur shutter is whisper quiet and highly reliable, like all Compurs.
Like all of the "b" and "c" models, it uses the dreaded EV (Exposure Value) system, which can be overridden, but still is annoying.
You can also swap the front lens element for a wide-angle or telephoto lens. With the two auxiliary lens, things slow down a bit (see info about the Retina IIc for an explanation).
The bottom-mounted film advance is somewhat of an oddity but certainly not an impediment. The viewfinder/rangefinder tends to be slightly dim but is still very usable.
It's a great camera for toting around on the street or for taking on vacation. Be prepared to answer questions of curious onlookers. Just tell them it's a classic and that they sure don't make them like this anymore.