I use the SMC-M 50mm 1.7 and the SMC-M 100mm f4 Macro on my K-5IIs and find them to be great lenses. The SMC-M 28 2.8 is good, and the SMC-M 150mm f3.5 adequate. I know another forum member here has written kindly of their SMC-M 150mm on their A7, so perhaps mine is a dud?
On the m42 side the Asahi Takumar 35mm 2.3 is very nice when I can get it focused. Surprisingly, my copy of the Helios 44m 58mm f2 is very nice when it's not facing any light sources.