Although we aren't a big site by any measure; we're using it and loving it for http://www.classlet.com
Quick question, a bit off topic. Here: http://twitter.com/Classlet/status/3854900110 you say "We finally rescued our Twitter user name from a squatter!". How did you manage to do this?
As per some instructions on the web, we created a "classlet2" Twitter account. When logged in, there is a help form where you can open a ticket. It took a few weeks, but they eventually released the account to us.