A Chinese website published one of the first reviews of the Intel Core i5-7600K, which is part of Intel's upcoming Kaby Lake platform. As you may know, Kaby Lake is the third generation on Intel's 14nm platform and expectations for performance gains weren't really high.
After putting the chip through a series of benchmarks, the site concludes the Core i5-7600K is about 9-10 percent faster than the Core i5-6600K. This is largely because the Kaby Lake chip is clocked 300MHz higher than its Skylake predecessor, on a clock-for-clock basis the performance difference is a mere 1 percent. The good news is that the performance increase does not come with higher power consumption, and that the integrated graphics is faster than before.
In its review of the Core i5-7600K, PCOnline found that the chip is about 9-10% faster than the i5-6600K, but that's mostly only due to its higher clock speeds out of the box (3.80/4.20 GHz vs. 3.50/3.90 GHz of the i5-6600K). Clock-for-clock, the i5-7600K is just about 1% faster, indicating that the "Kaby Lake" architecture offers only negligible IPC (instructions per clock) performance gains over the "Skylake" architecture. The power-draw of the CPU appears to be about the same as the i5-6600K, so there appear to be certain fab process-level improvements, given the higher clock speeds the chip is having to sustain, without a proportionate increase in power-draw. Most of the innovation appears to be centered on the integrated graphics, which is slightly faster, and has certain new features.