Currently, I use an optical cable from a BlueSound Vault to my external DAC, then analog cable into the receiver. I assume USB between Vault and DAC would produce some improvement but not sure I'd hear the difference. Hopefully its more than that which they're announcing.
@rongvk I don't believe you can use the USB as a digital output on the Vault. This feature was added on the newest version of the Node (N130). The Vault was not updated and is essentially the same generation as the older Node 2i.