The main reason I wanted to go with a rangefinder is simply the different shooting experience. I currently shoot with an Olympus OM-D, so physically it is already close enough the size of a film SLR. I'm still vary about getting an OM2 since I suspect the shooting experience might not be that much different from the OM-D.
Personally, I found there to be a huge difference in "feel" between a film SLR and DSLR.
My primary camera is an E-510. I'm used to the slight tactile feedback of the mirror flipping. Moving to my film SLR, a Canon AE-1, the sensation of taking a photo is positively industrial (I can hear FSU camera owners laughing). The mirror slap is (comparatively) very strong and loud. One of my main reasons for wanting to try a range finder (aside from the different focusing style) was to have a quieter camera.
The Yashica Minister I have is so quiet, and the tactile feedback so slight, that I'm not always confident the shutter has fired. I've tested it without film, and I know it does. But the feedback is similar to pressing a keyboard (read: very minimal). I don't fully trust it yet. It is so quiet that if people are talking, they don't hear the camera fire. I used it on Sunday for a friend's baby shower, and it was a breath of fresh air to have a quiet non intrusive camera. The DSLRs in use (not by photographically inclinded people for the most part) were very intrusive both with noise (not a big deal really) and light (lots of flashes going off everywhere). I'm definitely starting to feel the appeal of the RF.
While louder, I really enjoy my SLR. I like the focusing aid, it works very well (I wish my DSLR had something similar). I enjoy the huge bright VF. It is worlds apart from my E-510, or any entry level DSLR I've played with. I don't know how well it would compare to the OM-D.
Personally, I was able to afford two film cameras (my local classifieds have a half dozen film SLRs for less than $100 every day), and as I said, I got my RF for $50 on ebay). Despite similar lenses (50mm F1.8 and 45mm F1.7) I've set them up to do different things (Green-yellow filter on the RF for street photography; green and orange filters for the SLR to do portraits and high contrast outdoor/landscape stuff). This means when I rush out the door I only have to chose film vs digital; which film is already decided.
So, I guess what I'm saying is, I may be drinking the RF kool-aid, but I also love my film SLR, and they feel sufficiently different from each other, and from my digital kit, to make owning each worth while.