First of all, Michelle, I'm always impressed by everything you do. Thank you.
I just took a look at the latest alpha4 and I've found something very minor, but it's confusing. I'm using the Silver Bells style.
When displaying any of the views under the tabs such as "Active topics" (/forum/active, /forum/new, /forum/unanswered), the forum table (class="forum-table forum-table-topics view-table") is 100% the width of my content area, as I would expect. However, when I view the simple url for the forum itself (/forum/129), the table is not the full width of my content area.
So something about the calculation of the "sticky-header" table width is different depending on whether I view /forum/129 vs. /forum/active. It's certainly not critical, but could be an indication of another problem.