I am loving it. I downgraded my 6700k(really poor clocker. 1.4v for 4.5ghz) to a 6600k (really good clocker 1.3v for 4.7ghz!) and the single core performance difference is noticeable. Got it sat in a Fractal Design Mini ITX Define Nano and its a lovely little machine now over the monster sized (in comparison) h440 atx build.
I havnt had too much bother from the bios. Only got the board a couple of weeks ago so it might have an updated bios already. I should check!
You definitely dodged some issues buying it later, when I bought mine if you set XMP profile the board wouldn't even POST, then they'd fix that but M.2 drives wouldn't be recognised, the 'fix' for that would then break XMP again etc was a right mess! They'd even post new BIOS updates on the website only to pull them again a couple of days later, so obviously the board was released with major issues that should have been sorted before it went on sale. Either way, works like a charm now so will stop complaining lol
Damn, you really were unlucky in the silicon lottery first time round, the 6600k sounds very tidy though. My 6700k is running 4.6GHz @ 1.34v (iirc) on the main build but I'll leave the 6700k in this one at stock clocks, going for cooler temps rather than maxing test scores