The editor I require, needs to be easy to use. Even for people with absolutely no HTML knowledge
The projects I have tried are:
I've used both CKEditor and tinyMCE; I am using CKEditor now. If it makes a difference to you, I've needed to change the CKEditor source code on three occasions and each time it was a pleasant experience. The code is well documented.
CKEditor has released several versions in the previous weeks; the latest version fixed the problem where I needed to change the source.
I like the Telerik editor. It is not free, but it is very nice, and their support is great.