I run a forum over at http://SammyServers.com and I recently purchased and implemented arrowchat there. We usually have about 40-100 users concurrently online.
It works perfectly with my phpBB installation, and I've even put together some custom notifications, however, if I have the tab open for more than about an hour, page scrolling becomes nearly impossible, and all animated objects slow to a crawl. I physically have to close and reopen the tab to be able to do anything. I've had reports of this in all browsers, but it seems to happen more commonly in Chrome.
I only have one other ajax request running every 10 seconds to check for new PMs, and this never occurred before. I would appreciate some input.