It's been mentioned, but the memories of that year lost to RadEditor still haunts me.
On the bright side, they have an incredibly vigilant, and apparently numerous support-staff;
so whenever you need to find that little whatnot that's causing that particular day's RadBugs;
you know you can always have them brew up some custom and obscure mini-fix.
After one year of tangoing with that beast, I had to retreat to pastoral C64 GOTO adventures to preserve my sanity...
Alas, we all need our WYSIWYG editors from time to time, and after trying out both (F)CKeditor and TinyMCE in .NET settings, I am humbled by both.
Would choose TinyMCE at gunpoint though...