Peter Fisk is showing off a simple network game using Vista Smalltalk. He's integrated Jabber as well, which is neat. I found this interesting as well:

The mechanism for updated the remote player’s board is based on a special kind of text message. If a message is preceded with “@@@”, then the first three characters are discarded and the rest of the message is treated as a Smalltalk message. This technique could be used for collaborative work group applications as well as games.

That's a trick I've used myself in demos before.