Very useful. VNC lets you control other machines remotely, but setting up the server means faffing about opening ports in the firewall and such. UltraVNC runs things the other way round, which means it'll be easy to fix my parents computer remotely
This is why more politicians should be blogging: we get to hear about events first-hand rather than through the lense of the media. Tom Watson has posted his resignation letter from the Labour party, and Tony Blair's response.