first of all, many pros use this camera ... second, if there is a camera that becomes more popular in mamiya range now and in the future, that will be the 645 because of digital, this camera is better suited for digital backs.
the 7 is a very intuitive camera as a rangefinder/viewfinder should be .. in fact it is like having a leica M7 or zeiss ikon but a bit bigger and with much bigger film inside. the other alternatives of such a camera these days are far more expenssive or not as versatile as mamiya 7... examples, mint hasselblad swc, alpa system etc - more limited in some way, especially for general purpose photography, much more expenssive ...
besides the natural and intuitive viewing system (which some may prefer or may not)... the lesnes are supreme, especially superior in the wide angles... simply because it is not SLR ... so if u want a real lens with little compromise of optical aspects of photography, this is one of the best choices. and no SLR mamiya, rollei or hassleblad do not deliver that quality and plasticity in wide angle lesnes...
non relevant to apug, but i think i would really enjoy if this 7 system or alike (even in smaller size of 645) will be adapted to digital sensor as well... that way, i would have a rangefinder and a medium format quality...