Hi,
Yes, I've tried multiple WYSIWYG editors, including free / open-source
ones (and the telerik products that you suggested). I've personally
decided to go with telerik, mostly because they have most features,
the products has good docs and is commercially supported (important in
my case - they haev great support service). Most of the free editors
out there are not tightly integrated with ASP.NET in particular and
are mostly Javascript based which is not very convenient if you are
not very good with javascript and all the browser quirks. So yes, I
would recommend telerik yes, especially with their latest edition
where they have integrated "Firefox-like" spellchecking (very similar
to the built-in spellcheck in FireFox 2, however works for all
browsers).
Just my two cents.
~Kevin