Top 5 Free WordPress Themes of the Month — October 2012 Edition from Tom Ewer @ManageWP that design affects perception, is important and Tom’s article links to that information too.
“But whilst there is no doubting the quality of the great premium theme developers out there, you can find quality free themes. And that is the purpose of our themes of the month series — to unearth only the very best free and current themes available on WordPress.org” from that post.