Well chuffed with my new 9900K. Built my new rig over the weekend, 5Ghz all core overclock was no problem but I won't run it at 5GHz, I just don't see the need right now. I've settled on 4.2Ghz all core lock with Hyper Threading disabled which keeps temps below 60c at all times on my Dark Rock 4 in all the stress tests I've run, so plenty of reserve left in the tank in the temps dept. At 4.2GHz, in IPC terms, the 9900K is a dead match for my old 4690K @ 4.7Ghz, which could run everything I threw at it except games that obvioulsy needed at least 6 cores. Battlefield 5 was completely unplayable for example on my 4690K, it stuttered all over the place, but its as smooth as silk now.
Right now in 2019, a 5Ghz clock speed and an extra 8 threads are simply not needed in any of the stuff I use, but It's nice to know that as stuff becomes more & more demanding over the 3-4yrs I'll be keeping this CPU, I can up the clock speeds and turn Hyper Threading back on when required.
...covered for the next 3-4yrs in the RAM dept as well, 32GB at 3600Mhz means I won't need to think about buying more RAM as 16GB becomes the bare minimum requirement, which no doubt it will in time.