I have the 45/2.8, 55/2.8, 80/1.9, and 150/3.5 lenses. all are very sharp. The 80/1.9 is a cool lens, its main dissapointment being a bit more distortion than i'd like from a standard lens. The f2.8 version is said to be better in that regard but the 1.9 is the fastest 80mm for any medium format system. The 150/4 was reputed to not be as sharp as the later f3.5 version, but I haven't used the f4. I know my f3.5 is a great lens. All of the m645 lenses are pretty cheap.