My team recently reported that RakNet does not support IOCP and only runs on single threaded environment. Yes, using IOCP is server side problem not for client side though it is good to use same network driver model on both of the sides. Mostly it is for maintenence issues. Because as you know, IT IS MMOG! :-)
I guess RadonLabs used RakNet for their DrakenSang and it might be sufficient for P2P based multi-player game such as DrakenSang but not for MMOG.
So still need to hunt any good network framework for that...
A few years ago, for the age of N2, I designed network property(entity component of Managalore game framework) which uses OpenTNL. It was designed by me and written by John Smith. (Thank you John even he was willing to share it but not committed yet though) It have similiar problem to use for MMOG even though it is not so good to learn and understand due to have very steep learning curve.
It might be good if N3 has some very nice network module which widely can be used(it means scalability of the network engine) and is suit for any game genres even it is RPG or FPS.