My observations so far:
Default BIOS settings are quite good, no problems with it running between 4,8-5.0Ghz (Voltage does not exceed 1,3v, temp does not exceed 80C), depending on load. Have not yet started to tinker with OC as pre-installed Windows on mine was "bust" and I had to reinstall it from scratch using external medium.
It actually acted really weird, could not change user profile pictures, connect to Network drives, do WU, etc, etc...
So far so good, it performs like 9900k should and better than I could ever expect, considering form factor.
Also, it looks like there is not much thermal headroom left, to do any extensive OC.