The ability to issue broadcast wake-on-lan commands.
The DNS-320L works well as my always-on device and supports a choice of add-ons that can host VPN connections. Once connected remotely to my lan, however, it would be ideal to be able to wake up at least one of the dormant computers on the lan. Supporting this directly in the NAS avoids problems with routers that don't support WOL, switches that drop wake-on-lan packets other than broadcast ones (as they should after the destination IP ceases activity) and VPN software that blocks broadcast packets (presumably as it should).