In case you haven't noticed, BlogMatrix has a template system so if you don't like the "System" look and feel, you can easily install your own from the admin page. What's our template language? Simple: we use Blogger's "classic" templates. You can see the manual for these here. If you're migrating from a blogger account (or just have one) you can grab it from over there and install here.
Important: we don't work with new template language. If the file begins with '<?xml', it's no good to us (yet).
Hint: we're working on extending the Blogger template model to be more flexible for our needs. One good trick is this...
<Blogger n="50">
... which increases the number of entries shown from the default 20 to 50 (or whatever)
We'll probably be removing some functionality from the templates in the near future too. In particular, we're definitely removing "views" and we may be removing the ability to use the System 'frame' with your own template.