I got an M 50 1.4 with slow aperture blades for a price I couldn't refuse - just shipping
From playing with it, it seems like f2 is fine, but from f2.4 on, the slow aperture blades will cause exposure problems. Still, being useful at f2 and wide open should still give me a lot of ways to play with it, and I intend to compare it with my Rikenon P 50 1.4. It's my first Pentax 1.4 lens so let's see if it will get me excited enough to get it CLA'd.
Edit: actually, at f2 it only closes down half a stop (testing against the 2 second delay which will make the lens work fine - but I lose SR). f/2.8 and down, it stops the same 1/2 stop, so wide open an f/1.7 is all I get with this lens as it is...
I guess that means I get to compare it to the Rikenon 50 1.4 and the M 50 1.7
Luckily, from my few shots inside, it seems like it's sharp wide open!