My favorite camera of all time is my Mamiya 7II.
Second would be my old Leica M4 (talk about expensive!).
Third is my current Linhof Technikardan.

Truth be told, the Mamiya does have its shortcomings (what camera doesn't?). However, I have learned to "see" with this camera and find its limitations to be minor.

Pros:
- lightweight
- razor sharp lenses (noticably sharper than my old Pentax 6x7)
- 50mm + 80mm + 150mm covers practically every situation
- quiet (like any good rangefinder)
- did I mention lightweight?
- great "handling" camera -- like a 35mm
- bright rangefinder

Cons:
- limited lens selection (nothing longer than 210mm)
- 210mm is hard to focus
- expensive here in the USA
- battery operated shutter eliminates ability to do n-hour exposures
- forget about doing macro work
- wide angle and tele lenses require viewfinder to arrange, switching back to rangefinder to focus (reminiscent of my old Linhof Technika)

Overall a very fine camera. I'm sure the 6x4.5 fans can elaborate on why their cameras are better. Probably the best reason to consider 6x4.5 would be a future that would include digital backs.

Anyway I'm extremely happy with my Mamiya and expect to get many more years out of it.

Michael