I wholeheartedly agree with the appreciation for the Pentax-F 50mm Macro. One of the best Pentax lenses ever.
Unfortunately the ring for manual focus is a joke. Better to set the reproduction ratio first, then focus moving the camera back and forth.
I have different feelings for the ever popular 40mm Limited.
It's a Tessar Limited... but still a Tessar. Nobody, not even the sorely missed optical team that designed the Limiteds, can make miracles with those 4 elements in 3 groups
Contrast and flare control are good, sharpness is more than decent but not impressive (for a modern prime), bokeh is not ugly but not the nicest.
The lens is beautiful and a real pleasure to use, because it has much better ergonomics than the XS version (which is the only other pancake with AF).
Though I think that those willing to do without AF could get a similar performance from vintage Tessar pancakes, like the Pentax-M 40mm, or the Cosina-made 2.8/45mm or 2.5/40mm, sold at the time under various brands, and rather inexpensive today on the second-hand market.