Q: Your review of the iPhone 3G dock does not address the question of whether it will allow phone call audio to come out through the Dock Connector (ie, for those of us who have the Dock Connector to AV and USB cable).
A: Actually, the iPhone does not pass phone call audio out via the Dock Connector at all, regardless of the accessory in use. This is not a limitation of the iPhone 3G Dock or other accessories, but rather of the iPhone itself.
This also includes audio from other phone-related services like Visual Voicemail. Basically, any audio that normally plays through the iPhone earpiece will not be redirected through the Dock Connector. This applies even if you are using the iPhone in speakerphone mode—sound will come from the speaker on the bottom of the iPhone and not via the Dock Connector.
Note that the iPhone 3G Dock does include audio vents in the dock itself to pass through audio when used in speakerphone mode. Accessories that integrate with the iPhone for call handling such as the iHome iP47 (iLounge rating: C+) use the Dock Connector to handle non-call audio and a Bluetooth connection for call handling.