I always suggest Pentax users buy only original Pentax lenses. It is because if you want to use Sigma or Tamron or even Tokina, there is no reason to stay with Pentax, as those 3rd party lenses are rather limited in K-mount in both models and availability. So, why to do so, to get the worst of both worlds?!
Now, more and more compatibility issues have been reported with the latest Pentax bodies and/or firmware with those 3rd party lenses, here is a latest user report about (in Traditional Chinese) that the K-01 V1.01 firmware doesn't work well with his Sigma (17-50/2.8 OS HSM).
2. Reliability of the DA Limited Lenses
It is reported by a DA 40 Limited user that (in Simplified Chinese) the aperture blade of his new lens that has only been used for two months have had its whole mechanism self-disintegrated without any good reason one-day suddenly!
3. The Relation of Rolling Shutter and SR for Video Recording with the K-01
See what this Pentax user reports at the DPR. If it is really true, it is possibly that the processing power of the Prime M processor is insufficient to do both things well at the same time!
4. I am a Pentaxian!
Via DC Home Pentax Forum (in Traditional Chinese)
Wow! I have nothing more to say!! :-o