I've used JCK since I found them and have been thoroughly impressed by the quality of the product.
However, the last couple of updates have errored out with FOF error.
Nicholas from Akeeba found the problem is when Admin Tools is installed with it's framework (called F0F), the install script for JCKEditor incorrectly refers to it as F-oh-F (FOF), rather than the correct F-zero-F (F0F). I did the corrections myself and everything installed perfectly.
I've notified them and am sure they'll issue a fix shortly.