I looked into the pentax some time ago and actually I was more enamoured with the pentax 645N series than the 67. The 67 scared me, I couldn't tell what sort of megatripod I would need to work with it... I mean you hear kawhump! when that shutter fires. Anyway I ended up buying an rb 67 pro sd. And I have even used it handheld with MLU (not recommended but doable).
The RB is a great buy with a wonderful lens selection. I have everything from a fisheye to a 360mm and 2x TC for mine and there is also a fine 100-200mm zoom. The big attraction of the rb, to me, was the rotating back and also the great selection of affordable rollfilm backs- 645 to 6x8. For 6x8, there is a nice motorized back. I also have done quite lot of polaroid with it. Just so you know, I had my rb and used the waist level for about a year before I discovered the merit of the metering prism viewfinder, and I have used that ever since. It's much easier to work outdoors and more quickly with that.
Recently I am not usig my rb much, in favour of a much lighter field camera, a horseman VH, which shoots 6x9 cm. I have lenses from 90mm to 360, and it offers surprisingly extensive movements. I now use the VH with an angle viewer and it also has a rotating back. In my opinion, 6x9 is very nice for landscape. The VH also takes all my rb backs, a nice benefit! Plus the VH, even with a few lenses added, weighs far less than the rb.
You might find some useful (albeit aged) comments on this site:
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