For the first time since moving over to Vista, I've just tried to use telnet, and was surprised to receive the following response:

'telnet' is not recognised as an internal or external command, operable program or batch file.  

Yep, it seems the telnet client has been removed from the default Vista install!  Fortunately, it's pretty easy to get it back - just go to "Programs and Features" within the Control Panel, select "Turn Windows Features On Or Off", and scroll down to the Telnet Client checkbox.

Give me my telnet client back now!