I upgraded from a 2600k to the 2700x about a month ago. Can't say I've noticed all that much difference, day to day use is generally the same, and I don't play with FPS counters either, and I game at 1080p with 144Hz monitor, and everything looks and feels smooth. However it felt pretty smooth anyway with a 2600k. This really is a testament to the 2600k being such a good processor.
I just had the itch bad and wanted a newer platform, but it was very much a want not a need. Also, there were a few fringe cases where my 2600k was struggling a little bit, not in gaming really, but when running a webcam chat in discord whilst gaming, that would max my old CPU - or if people connected to my plex server and transcoded things whilst I was in a game. I also play they are billions sometimes, and when the hordes got quite large, I'd noticed it struggled a little too. Interestingly I've not done any of that since my upgrade, so time will tell if it was worth doing for those cases or not.