http://www.pentax.jp/english/support/download_digital.html
And the changes for the new firmware are as follows:-
- Optimized contrast AF when using [HD PENTAX-DA 560mmF5.6ED AW] lens.
- Improved stability for general performance.
Update (2-1) : I have roughly tested the LV AF of my K-5 after updated to the latest firmware and it seems that the AF is faster now and the way the camera is searching for focus is different, i.e., the algorithms have been revised. This is especially obvious for telephoto lenses, for what I have verified with my Pentax 300mm AF prime.