My Pentax SV is an absolute jewel. It is as smooth and nice to work with as any camera I have ever owned. The only problem I ever have is that the shutter is not real fond of very low temperatures.
If I feel the need for a built in meter (usually in low light situations) I grab my Spotmatic ESII, but I usually prefer working with the SV.
My favorite M42 lens, probably of all time, is my Pentax Super Tak 50/1.4.