I am just as impressed with its image qualities as I am by any quality optic. I used it quite a bit before I got my own RB camera (an RZ model one), but I never got my own because I like the focal length and the maximum aperture of the RZ 110mm better.
If I had an RB, I'd probably be more inclined to either go down to a 75 or up to a 127 for my "standard" lens. Strangely enough, while I love a normal lens for 35mm hand held shooting, I don't seem to care for them that much in the larger formats shot on tripods. I generally prefer a standard lens that is either slightly long or slightly wide when using the larger formats. For instance, a 105mm on 6x6, or a 210 or 240 mm on 4x5, or the 55mm on 645.