Had an R3A I just sold. I only sold it because I want a R2A.
The R3A is great, the build is good, it is a solid camera and works just fine. The finder is fantastic for 50mm. The shutter sound is a bit clunky, actually more like a slap but still much quieter than any modern electronic SLR. The operation is just fine and it works just fine with any M lens you can throw at it (I had a 50/2 Zeiss).
I've only fondled a Leica and yes it did feel nicer but in the end I got my R3A for £250 which is nothing compared to Leica prices plus you can change film without dismantling the camera. The meter worked just fine too. Overall a great little camera and the only reason I sold my R3A is because I want a 35mm lens and the R3A goes only to 40mm (which is actually a bit of a stretch to see). If I was shooting primarly a 50mm shooter I can't think of anything better than the R3A based purely on the viewfinder (maybe the M3 is better but I wouldn't know, never had one).