There are a few limitations, of course. This is an early version, after all. Besides the issues Peter notes in his post about WYMeditor, here are a few more things I noticed:
Table accessibility. There is no way to add elements and attributes (th, caption, scope, etc) needed for accessibility to data tables.
Table resizing. It is possible to size tables by dragging handles. Doing so is reflected in the markup. That needs to be filtered out at some stage before saving the page to the database.
Incorrect nesting of lists. When you create nested lists, the current list element is closed before the next level ul or ol is inserted.