Downloaded and installed here. There's no great differences that I've noticed so far. It's perhaps a tad more responsive but the battery doesn't seem to last quite as long as previously. Apart from that I've had no problems.
Battery life apparently better here too, but I hate that Android KitKat ruined the wake lock detector apps I was using.
As for the rest, I must say the difference in performance is more significant than I expected. The way the phone wakes up, unlocks, starts apps and how smooth everything is now is certainly an improvement.
By the way, any fix to the SD card problem? Seems like writing to it with anything not Samsung fails, but I simply cannot stand the Samsung file manager... Anybody knows how to fix this?
I have noticed a huge difference in battery consumption when location settings are set to accurate, which is a must for navigation. When set to power saving, it seems to be better at managing the battery, but with high accuracy, it seems to be way worse than with android 4.3.