I mentioned some of the limitations of rangefinders in my earlier post. IMHO, those are the most important, although there are others. For instance, you can't see the effects of special-effects filters (star filters, polarizers, etc.) in the viewfinder. (That can cut both ways, though; as Andy mentions, dense filters, such as thick ND filters, can make an SLR difficult to use.) Parallax is an issue with close subjects -- that's a good part of why rangefinders are poor choices for macro work, but parallax can become an issue even in close but non-macro photography. (Some rangefinders have parallax correction marks in their viewfinders, but this isn't universal.)
As to examples of good rangefinders, that's a hard one to answer. Leicas are often considered the "gold standard" in rangefinders, but they vary a lot in age and capability. Most Leicas support interchangeable lenses, as do some Contaxes and clones of both of these lines. Other rangefinders are much more basic, but still very capable for what they are. In the 1960s and 1970s, small fixed-lens rangefinders like Canon's Canonet line were very popular cameras. These cameras had automatic exposure and were generally easy to use, but lacked the flexibility of an interchangeable-lens Leica. Some of them had very good lenses.
If you say what you want to do with a rangefinder, I'm sure you'll get more specific suggestions.
