There is no such thing as rangefinder-style-work or rangefinder-ethos. Its simply a different designed camera that shoots pictures like any other camera. We also have people referring to cameras as "rangefinder-style". Its basically a misnomer for people trying to describe retro-designed cameras that are sans-mirror, compact, and mimic the squarish body of rangefinders of the past. These are usually mirrorless cameras such as the Olympus Digital Pens and Fuji (Xpro, X10, etc). (the funny thing.... shooters who are really into rangefinders... not the owners of talking items/attention... generally avoid using such terms because they are so inaccurate)
The main difference, as tirediron already pointed out, is the focusing mechanism. What is important is that it changes the way you "see" the world and compose the photo which DOES impact the flow of work:
* Smaller.. discreet.
* Garnishes less attention and is often less "threatening" to the environment. It is an attempt to address the whole notion that as you try to document a situation, your presence changes it.
* Optical design for lenses are also affected because of the short film-flange distance.
* The viewing optic is separate from the picture taking optic. In other words, this is not TTL composition.
* The viewing optic has infinite DOF at all times. It makes it easier to see the subjects in frame forward to back without being subject to the lens DOF.
* The viewing optic's focal length (magnification) is generally wider than the lens. The framelines are markings in the viewfinder that indicate the frame of the picture taking lens. You can easily see subjects entering or just outside of the frame. Makes for just in time adjustments to composition. Think... walking around, arms extended, fingers forming a box, while you compose a frame with your fingers... much like you see videographers do to try to visualize the scene before actually shooting it.
* Due to the viewing optic, the photographer is not subject to "tunnel" like vision/experience as TTL camera designs. Its less intrusive mentally as you bring the camera up to your eye and bring the camera down to view the world with your both eyes. Everytime you bring that camera to your eye, its the same magnification and same view. I can still interact with the world, walk around, reposition myself, etc without falling over tripping over myself.... even with a telephoto attached.
Its kinda hard to explain and >> it certainly doesn't fit everyone.<< For me, I prefer it. Its more fluid... feels like an extension of my vision rather than something that dominates it. I have to visualize what the photo will look like without actually it dominating my visual experience while I create the photo.
There's a whole list of reasons why the SLR has become more popular....
* TTL gives you What You See Is What You Get.
* The photographer relies less on "visualization" because of WYSIWYG
* Versatility. Macro and long telephotos. The rangefinder design is limited to its base length.
* Auto focus.
Note: A correction to tirediron's response. There are rangefinders of fixed lens design. Example, the once really popular Canonets.