I bought an R2A in March to back up my Leica M6. I have so far used it with the Leica lenses.
It has a shorter rangefinder base (significantly) than my M6, so I do not use the very fastest lenses with it. It focuses fine at moderate distances with the 90mm f/2 that I have, which is the severest test I've put it to.
The aperture priority meter is a great convenience, which I think I will use extensively for night shooting and available light. Outside, with lots of sky in the pictures, I have used it in "metered manual" mode almost as much as full auto. The metered manual mode is very easy to use, too. The viewfinder shows the selected shutter speed in solid lights, and in blinking lights it shows the "preferred" speed that would have been used if you were in full auto. That gives a very clear and instantly comprehensible picture of whether you're over or under and by how much.
It is quite a bit noisier than the M6, but isn't everything? I agree that for $500 it's a great buy considering you can use so many lenses, including the best in the world. It feels great in the hand. It has a nice raised area on the right and a non-slip skin, so it's easy to carry in your shooting hand, which I like to do rather than have a camera slung around my neck all the time.
When I go out with both it and the M6, it's the R2A I use more. That'd probably be true if I had an M7 and M6--I'd use the M7 more. This way, though, I have spent about $2300 less on the camera body.
One con: As I mentioned in a different post, the shutter mysteriously jammed up completely on me after less than a month's use. Time will tell whether this is a fluke or a sign of more trouble. The camera was replaced immediately, so I'm still happy. After this experience I expect to stay happy but do not expect it to last for 50 years. There will come a point where it ain't worth fixing, whereas I doubt that the M6 will reach such a point even if the Leica company vanishes. But that's another story.
I told you the con, but I want to send you a strong buy signal!