Question for Pentax experts regarding lenses

I'll second the SMC-M 28mm f/3.5 , really sharp and a pleasure to use.

Also the SMC-M 50mm f/1.7 is very good, just some minor defects (flare in certain conditions, coma wide open, nothing major).

I really like my SMC-M 100m f/2.8 & 200mm f/4 , two lenses with one of the most creamylicious bokeh I've ever seen...

All those lenses have little to no distorsion on APS-C.

I know, I can correct distorsion (& vignetting) on my kit 18-55mm with a click of the mouse, but I really like when photos just "come out", with only minimal adjustments done to the raw file. When I need to churn it, boost it, scratch it, straighten it, lighten it, it just makes me feel very depressed...

I also have a M 55m f/1.8, no big deal, fringes, etc. you can safely steer clear of that one.
Regards.