I have more than 30 pfsense runing at my clients office or datacenter. From 1 to 100 mbits. Every site has a two nodes cluster, built on HP proliant system or IBM Xseries, form 100 to 5 000 users behind the boxes.
First machine has been started in october 2005 (v0.69 I don't mistake myself).
All systems are runing basic features (IPSEC, pptp, captive portal and multi wan). For example, I have a cluster protecting medical applications (9 J2EE clusters) processing data for 750 000+ patients.
I'am starting a new project wich will use the squid+squidguard packages in addition to the other basic features, in this project I will deploy pfsense boxes all over the world (europe,us,asia,africa), that's why some of you have already heard me speaking about a management host on the IRC channel. On another project, I am going to change openBSD based pf firewalls to pfsense (European country military context).
I love pfsense and its developers team. The project is awesome.