Brian,
Here's one person's take on the M series cameras, with a lot of the minutiae that accompanies them.
http://cameraquest.com/mguide.htm
I'd suspect frameline sets, finder magnification, and metering (or lack thereof) are what might make the most difference for you. These things all vary by model and sometimes within models.
My rangefinders and SLRs advance themselves via Pavlovian response. When my brain registers a shutter firing, my right thumb twitches.

You rarely see a Leica rangefinder used with a motor winder, as it's somewhat antithetical on a small, quiet camera. You also might find the film advance on a Leica is smoother and requires less effort than you're used to. If you want to get to the next frame a little faster, try the trigger-winders mentioned, but I'd agree with SteveS on doing without initially.
I love a 1:1 finder (shooting with both eyes open and a floating frame), and so am mostly using a Bessa R3A now, with a trigger winder (for speed, stability, and a better fit for my large hands) and assorted lenses from Leica, Minolta, and Cosina-Voigtlander. (The 1:1 finder doesn't have framelines for lenses wider than 40mm.)
I'd suggest reading up a bit on specific features, pondering your expected usage, then asking a few more questions before you take the plunge.
Lee