Just been out in daylight shooting with K120 and M135.
The K120 is better indoors.... but outdoors is a different story. I found the differences in IQ totally insignificant. In fact, the M 135 is a little sharper when focused close to infinity. This does not mean that the k120 is a bad lens though. However, after taking many many shots I realised that holding the M135 was more comfortable. I just seem to get a better grip with it. I will test a little more but I have a feeling that the K120 is soon on its way to another owner. This gives me an excellent opportunity to buy the K 135mm F2.5 and make a new comparison with the M135
Update: I got the chance to test the K 28mm F3.5 today as well. OMG what a lens! Not too good wide open but already at F4 the sharpness is very very good! At F5.6 it's truly excellent. The bokeh is also surprisingly good. I love this lens!
Kind regards
.lars