I have the blued 4-5/8" Convertible. It is a great little gun with a wonderful balance and nostalgic looks. It's very tight and well built. I mostly shoot .22WMR through it, because .22LR is just a lot more fun out of my Ruger MKIII. Plus, I like the looks of the unfluted .22WMR cylinder better.
Also, I think the WMR is a tiny bit more accurate out of my Single Six than LR. I've heard this about most convertible revolvers (.357/9mm, .45LC/.45ACP, etc.). The slightly larger diameter of the bullet and shorter jump to the forcing cone of the bigger cartridges means tighter tolerances and therefore better accuracy.
I originally bought the Single Six as my "kit gun". A rimfire revolver that I could pack away into a hiking rig or camping box for survival/plinking purposes. But it mostly sits in my safe and fulfills my "cowboy" category. It has also become my "beginner's gun", that I use to teach a new shooter the basics.