Tom's Hardware Guide published a review on Overclocking Intel's Core i7-7700K: Kaby Lake Hits The Desktop A quote from the article:

Intel's new Kaby Lake CPU delivers on the clock speeds the company promised, but the power consumption and thermal characteristics were disappointing based on a leaked sample of the new chip we received and tested weeks ahead of its official launch.

 Overclocking Intel's Core i7-7700K: Kaby Lake Hits The Desktop @ Toms Hardware