I work at Automattic doing development and VIP support for WordPress.com. I've also written a ton of WordPress plugins (the most of anyone on WordPress.org last I looked).
Stuff said here is my own personal opinion.
20 How do I turn off self-closing tags for markup in WordPress (for HTML5, or HTML4, for example)? Aug 11 '10
14 how to reduce the number of spam comments Aug 11 '10
9 Can I rename the wp-admin folder? Aug 11 '10
7 wp enqueue inline script due to dependancies Aug 3 '11
5 Large Uploads in WordPress Mar 7 '11