I've noticed one little quirk, but I don't know why it is happening:
When I have any kind of < script > within the FCK Editor, and I submit it (via XMLHttpRequest), if there was a '+' sign it gets stripped out of there. But if there's a + sign not within a < script > tag, then everything is just fine. It even does this with the built-in FCK Editor E-mail Guard (removing the '+' signs).
+ Sign taken out when Submitting