My Dating and Attraction Blog uses WordPress. I've recently switched from Joomla!, and guess what: the header tags aren't set sensibly in the default theme. In particular, article titles aren't wrapped in <h1> tags because the blog name gets put there.
I've made some hacks to the default theme to fix this. I'm not a guru at theme hacking, so my fixes may not be ideal, but it'll give you the idea.
Joomla! doesn't get this right be default either. It makes no sense to me when content management systems don't follow basic SEO rules out-of-the box. I hope this gets fixed in the WordPress core, because having good SEO out-of-the-box would give WordPress a compelling advantage over the competition.