I get told often that the forum here is not useful because it can't be searched. I haven't had that problem yet, so I thought I'd share how I do it:
In the header, in the top-right corner, there's a -not very obvious- search box that says "search wordpress.org". I type "wordpress.org/plugins/s2member/" for relevance because it's added by the site at the end of every opening post in the forum, followed by the keywords I'm searching for, and hit enter.
I used to just add "s2member" for relevance but, although it worked, I also got a lot of results from outside the forum too. So I now made it more specific using "wordpress.org/plugins/s2member/" and it's been working very well for me.
To search our old forums, you can use this page: http://www.s2member.com/quick-s.php
I hope that helps you find what you're looking for. :)