my site is a fairly heavy custom wp build, with around 50,000 articles and 20,000 + registered users. Since we installed wp super cache the site has been performing amazingly under load (better than any of the other caching plugins, tried 'em all so well done for that!).
However... we're getting whole site crashes pretty regularly (every few hours) which are only rectifiable by renaming the wp super cache folder via ftp, and then reverting to the correct folder name when live.
We've got the site running over 2 x quad core machines, i've increased php memory limit and defined WP_MEMORY_LIMIT.
Site is at http://www.c21media.net, and I'm happy to pay for your consultancy services in getting this running properly asap. Please contact me dave [at] brandydigital [dot] com. thanks in advance or Skype @pluggyboy.