I have always been a big fan of desktop charging docks for mobile phones. I have purchased them for most of my recent phones and they are quite handy for being able to quickly charge a phone without hassling with cords.
I bought the dock for the Nexus one and have been using it for a few weeks not and just recently connected the audio out jack to my Bang & Olufsen stereo in the bedroom. The dock itself was nice without the audio but the addition of the audio brings this dock and the phone to a new level of usefulness.
When the phone is placed in the dock it automatically opens the clock application making it a very useful bedside alarm clock. From the clock application there is a direct button to the mp3 player. When the phone is in the dock it automatically pairs with the dock via bluetooth and provides a high quality audio signal to the bedroom stereo. Since the connection is bluetooth wireless the phone can be removed from the dock and disconnect from the audio system with no popping or other noises that one might get with a physical connector.
With the thought and attention to detail of the dock design and clock application one has to wonder what the Nexus one Car dock is going to be like. I have already seen the "car home" application on the phone but one has to wonder what kind of integration the dock might have with the car's audio system.