I have no complaints about the bokeh from my Mamiya 180mm f4.5 for my RB67. But that's a different animal than the Mamiya 7 or a Fuji rangefinder. But I do agree overall with msbarnes - the bokeh king in hand-held medium format is the Rollei f2.8 lens.

Both taken with a Rollei 2.8E with the Planar lens.