I have owned the Kronos for nearly 2 years.
The sounds are awesome.
KARMA is so inspirational.
Tweaking is sometimes a nightmare - only because there is SO much to understand. Korg have some nice tutorials on YTube and there are others you can buy, but this is by no means a "simple" ready-to-play keyboard - yes you can play it straight out of the box but you'll be fiddling in no time - mainly because you can!! The real-time control surface sliders/buttons etc are amazing particularly coupled with and when playing with KARMA enabled.
My personal "con" is the CX3 engine which is very very nice and usable but not like a real CX3!!!! And the rotary is lacking a bit - needs a lot of tweaking. Ksounds have resolved that for me by offering a set of nice configs called "Organimation" and well worth the money IMHO - these are NOT samples but deeply edited configs (hence new programs) including vastly improved rotary configurations. (I ended up buying a Roland VR09 just to keep my "B3" addiction alive!)
If you want to save some money, find a Kronos, install an extra SSD and 1GB RAM (at worst $200) and hey presto, you have a "Kronos X
All the best