I currently have 3 units. 2 are running Raspbmc and serving up XBMC Frodo to the main/bedroom TVs. The third is running Wheezy and pywws to automatically tweet my weather station data every hour (check it out @SumnerWeather).
These little things are great - so cheap and with so much potential.
I came across the PiFace add on the other day - and am eagerly awaiting its release. That should make interacting with the outside world much easier.
I am also eager to try out SiriProxy on another (yet to be purchased) device. Would be great to pull up to the house and ask Siri to open my garage door...