If you haven't already bought it, I'd agree with the other people who say "suck it up and get the M6." I started my RF phase with a brand new R2M. I was looking for an R3M due to the 1:1 finder, but couldn't find any at the local shops in Seoul. I went with the R2M, and loved shooting with it. It's a great camera as long as you're a believer in the addage "it's just a box to put film in." Yes, it's true that the lenses are vastly more important, but I also like the feeling of manual cameras. The R2M had a film lever that felt like a broken nutcracker every time I wound it, and while the shutter isn't really all that loud, it is a pretty distinctive metallic *CLICK*. I ended up deciding to sell mine before the body got too ratted up and it lost too much value.
The Bessa's are very capable cameras, and if you never hold a Leica, they will treat you just fine. I would buy one in a heartbeat as a backup if someone offered me one. They're very lightweight and have a wonderful finder.
I got an M4-P after I sold the Bessa, and after a CLA, it's beautifully smooth (mine has a brass top plate and brass gears, as it was one of the really early ones). The two biggest reasons I swapped were for the whisper quiet shutter and the resale value. You can basically lease a Leica for nothing, since their values have gotten as low as they're going to. Buy one, use it for a year and don't mess it up too cosmetically, and you can almost always sell it for the price you paid for it, if not a little more providing you're a savvy buyer.
The M6 is basically an M4-P with a meter, as far as I know.
Easy way to break it down:
Bessa R3M - 1:1 finder, trusty, reliable, capable, but not polished feeling. Strong chance of always thinking "wish I had bought the Leica"
Zeiss Ikon - better build quality/feeling but not fully mechanical. Best finder of the bunch.
M6 - amazing tactile pleasure (which some people don't care about), most expensive initially, but you won't lose any money if you decide to sell. Least likely to sell due to nothing worth upgrading to.