Congratulations on the work being done on 0.9. Thematic is getting better and better!
To my suggestions:
1. HONOURING CUSTOM DATE FORMAT
Thematic does not use the date format set in Dashboard > Settings > General. (I can try and submit a patch for review if you are interested. I’ll just copy the code from a theme I trust, like Sandbox, Simplish, or Tarski.)
2. USING AUTOGENERATED EXCERPTS AS META DESCRIPTIONS.
If a post/page has no explicit manual excerpt, it may be better to not add a meta description at all. I recently posted a request about this on the HeadSpace forum:
Note the Matt Mullenweg quote. It is interesting.
The manual Excerpt in WordPress. What, why, how, tips and plugins
I did a little research on the subject while writing this and, while there is no way to tell, other than extensive testing, I tend to believe that AUTO-generated meta descriptions are not a good idea.