The RasPi is nice but it's also not terribly powerful. It definitely has its limits. For example, I found out the hard way last weekend that trying to run an Etherpad-Lite on a RasPi is a great way to run one into the ground...
I have a RasPi Model B Rev 2 running etherpad-lite and a Tor-Relay. Slow as shit, but it works. :-)