I think it's important that we get as much info from users as possible regarding the scalability of phpfreechat in various types of setup.

Chatroom, phpfreechat, and irc-setups all have their own separate benefits, but one of the things which must be weighed carefully is expected number of concurrent users and the scalability of the app. So far I haven't seen any reports from chatroom or phpfreechat re. the number of concurrent users.

One thought for those with scalability problems and a large number of modules: You could create a fresh install of Drupal on a subdomain with user tables shared and only the modules activated for the bare essentials, and then embed the chatrooms via an iframe - this way you would still have control over users and be able to determine permissions, which is the main reason for using Drupal chat instead of irc or a third party flash chat service.

(similar request for scalability information has been posted at chatroom module at http://drupal.org/node/807460 )