We're planning to switch our forum from phpBB3 to SMF. We've used phpBB since 2001 and our forum has now 30.000 registered users and 2.200.000 posts. Google Analytics measures approx. 45.000 to 50.000 unique visitors per week.
Not sure if that is a lot for SMF or not. Our phpBB is running on a dedicated server with Hexa-Core processor and 64 GB RAM. PHP is configured with 96M memory limit and uses APC caching.
Now I'm wondering if this is something SMF could handle "out of the box" or is there some settings that should be changed?
SMF runs large forums well. some tweaks may be required.
for example see http://warriorcatsrpg.com/
and look at http://www.simplemachines.org/community/index.php?topic=293441.0
also large forums like yours should use sphinx for the search daemon, if you do convert you can request access to the big boards group in your profile to get access to the info about sphinx.