I think you are right there is something about certain 50 1.4s that is problematic with very early pentaxes but I cannot recall the details.
I own several of these "pre-Spotmatic" cameras. To my way of thinking they are one of the prettiest classic SLRs. In fact they remind me of the Leica screw mount cameras in the hand (with the obvious addition of a pentaprism).
As to lenses, basically you cannot go wrong with any takumar, super takumar, smc takumar etc lens.
I happen to like using the very early ones that match the camera. The preset longer lenses (105 and 135) and the semi auto takumars that have to be cocked before using are interesting lenses.
My favourites would have to be any of the 50s (f1.8/f2.0 and f2.2). All perfrom well but the later f1.8 is stellar and has lovely bokeh.
The 105mm (all of variants are superb if you want a nice and fairly cheap portrait lens - these go for less than the 85mms.
In the 35mm range you cannot go wrong with the 35mm f3.5 but if you find a nice f2 35mm then grab that as well. Both are excellent. As I might add is the 28mm f3.5.
Most of these lenses went thru a few versions (most later lenses have 49mm filters. Some early ones had 46mm and a few had 58mm but later reverted to 49mm) and I have never been disappointed with any of them even though some of the later ones are probably technically better (multicoating etc) They are just bloody good lenses. Bear in mind they do not have excellent flatness wide open of field so are better in the centre than on the edge (as you would expect from a consumer lens.) But having said that they do tend to be very sharp in the centre.
Check out this site for some user reviews.
http://www.pentaxforums.com/lensreviews/
Here is a photo I took a few years back - essentially a candid shot of a stranger on a bus. Taken with a 105mm (I do not recall which version but have a sneaking feeling it was an early preset one as I recall I used it on a digital camera with adapter and the preset works well in that situation so thats the one I mainly used) I would say this is more or less what you can expect from any takumar lens of this era. If I said I had shot this with Leica glass I would be surprised if anyone said it were not. The colour, the rendering, the sharpenss is spot on.
