Kunena worked for me almost out-of-the-box, having luck with Kunena default colors matching perfectly my Joomla template..
However, end-users of the site don't know or want to learn BBCode at all. Kunena doesn't even support a mimimal WYSIWYG editor having a user-friendly GUI where people make text bold by selecting it and clicking a "B" button, having the code behind generating a [b]text[/b] code. This is a CRUCIAL aspect of usability in my opinion which undermines the value of the whole Kunena projects.
On Kunena forum people are asking for a WYSIWYG editor since longtime and my frustration is increased by the answers they get.