I can not say enough of performance gain that my site gained through migrating to Pressflow + Varnish. However I have a rather annoying problem with Pressflow. After migrating to Pressflow 6, the statistics of online users does not show correctly. For example the forum shows 70 online users while there are actually over 1000 users online.
I am wondering whether it can be fixed or it is just a "collateral damage" that one should afflict to gain the performance. If it can be fixed, appreciate your hints to do so, and if not, how else can I show the correct stats.