I've had a heavily modded phpBB message board up and running for about a year. I use it for private RPGs, RPGs that have "content issue" and aren't allowed at Myth-Weavers, and as the base for my chat games.
For real-time RPGs, I'v been using an "RPG Chat" page of my own creation. It has an AJAX based chat box that parses my dice roller BBCode and an iframe to display the map. I make my edits in Photoshop and then publish directly to FTP. So far, it works well . . . better than most of the currently available virtual desktops.
Perhaps Battlegrounds will make me change my mind.
I am excited to see that phpBB 3.x is on the way. It's practically "full featured."