A minor problem I noticed -- after getting the admin.mambot (google for "Restricted access JCE" and you'll find the fix; a link to it can be found in the forum for this add-on) fix in -- is that when I was editing a post I made with the TinyMCE editor, everything was centre-aligned, and had to align everything left again. It was probably due to some minor thing like the code written by tinymce and jce's editing.
Now if only these things were 100% standards compliant, I would recommend them totally. Thankfully the authors of these editors are paying attention to this sort of thing now, and are either 100%, or getting there.
Finally, JCE is probably one of the better ones out there, so yeah, if you want to use one of these, this is OK :).