I love shooting with my IIIc and Canon IVSB2. They're beautiful robust works of mechanical art, and they can easily slip into a coat pocket. I find that one or the other is my preferred carry when I want a compact shooter, such as on a long walk or a backpack trip. I can't say that I enjoy shooting them more than my M2 or M4-2, but I enjoy them as much. Shooting a Barnack is a slower process for me than shooting with an M. I prefer an M for street photography, and a Barnack for landscape work.
FS: Zeiss-ZM Planar 50 plus hood, Pentax MX, Voigtlander Ultron 40/2.0 SLII in Pentax K-mount, Takumar 100/2.8 and 35/3.5 lenses: See my ads in Classifieds
M3, M2, R2A, IIIc, IVSB2, & T, and assorted LTM & M lenses
Minolta XD11, Pentax ME Super, and assorted MD Rokkor and Takumar lenses, Rolleicord III, Rolleicord Vb, Rolleiflex Automat MX-EVS