I was looking for a good editor too last week, tried WMD but is just not easily customized enough compared to markItUp. It's so easy to extend and customize markItUp, function-wise and theme-wise.
OpenWYSIWYG was on my list too but after trying markItUp I got stuck with it. Plus OpenWYSIWYG is not jQuery, it's JavaScript, but open-source and cross-browser.
