The number of pages served changes from month to month (of course) but the fluctuations were too minor to be the cause of my bandwidth utilization going down.
Just about everyone on my forum who was familiar with the Classic board has said that Threads is several times faster. I allow unregistered users to search my forum (lots of PC and networking info) and the searches were slowing down Classic really bad. Searches don't seem to impact Threads as much (must be the MySQL back end).
Some of them complained that Threads didn't have the same features as Classic, but it’s easier to hack features into Threads than it is to hack Classic (IMHO). I've made a lot of changes on my own, and I don't consider myself to be a PHP “scripter”. I think if you've had some exposure to CGI, Perl, etc and you know HTML then Threads is easy to modify (very efficient use of templates).