Thought I’d add a voice to the minority opinion…
I prefer SLRs to rangefinders for similar reasons to one other person in this thread - accurate framing being the most important consideration for me. I know exactly what I'm getting in the frame when I take images with my SLR, whereas when I shoot with a rangefinder, I am often surprised when looking at my negatives on the light box to find that my images on the film do not match up with the way I remembered seeing them at the moment of exposure. Composition is one of the absolute most critical aspects in making a photograph, especially on the street with little or no time to prepare, and the SLR is just way more accurate at providing me consistent results. I also enjoy being able to actually see what depth of field I have, and I am much faster to focus with an SLR – I like how the image just snaps into focus, whereas with the rangefinder I have to check and recheck my focus if I think it is critical. That said, lower quality SLR lenses can be difficult to focus, but with higher quality lenses, they snap into focus very nicely.
Mirror slap doesn't bother me at all - people talk about it like it shakes the camera in your hand like it's a running engine or something - I've done lots of handheld shooting at 1/4 - 1/30 with both SLRs and rangefinders, and see no difference in the results - the movement of the subject (I rarely shoot a purely static scene) at these speeds is going to blur the image anyway. Or, unless you brace the camera against your body, a light pole, or whatever is available, hand shake is going to be more of an issue than mirror slap in blurring the image.
Faster lenses are a bonus for rangefinders to a point, but the one or two stops gained could be made up by pushing my film or lowering shutter speed, plus most super fast rangefinder lenses are prohibitively expensive for me to buy, if I want to buy what is considered the best in rangefinder lenses. My SLR Nikkor lenses are considered some of “the best” (please let’s not get into it) in the SLR world, and yet they are pretty cheap on Ebay.
Also "mirror blackout" is not a major drawback for me either - honestly, even 1/60 of a second is such a short time to be "blacked out" that I doubt it really matters as much as everyone thinks, - I mean, it's basically like blinking. For Art, product, wedding or travel shooting, I don't see how continuos viewing is a great advantage. If stopping fast action is what you need to do, as in sports photojournalism, you’re not going to be using a rangefinder anyway. You’re going to blaze away 25 frames in a couple seconds with a DSLR.
Of course I can’t deny that rangefinders are lighter and quieter, they are nifty looking, and I enjoy using one occasionally. But the only practical advantage outside of weight and shutter sound that I can think of is that I use yellow filters often, and it's nice to have a non-yellow image of the world through the viewfinder, as I do with my SLR. Then again, I'm usually shooting black and white so I'm not thinking in color anyway.