I love Markdown and use it for all my blogs independent of blog-system (I currently use WordPress, Serendipity and b2evolution and Markdown is perfect in that sense). It’s lightweight and beats any WYSIWYG editor on the market ;) There was a Markdown plugin for b2evo, but it didn’t work with the new plugin API (and the author hadn’t updated the post since 2004) so I decided to make one myself.