at the moment their is only a dos proof of concept, but i smell soon a exploitable shell version of this. This is gonna hit hard like DCOM did with the blaster worm(s).
* Messages are delivered to the Messenger service via NetBIOS or RPC. If users have blocked the NetBIOS ports (ports 137-139) - and UDP broadcast packets using a firewall, others will not be able to send messages to them on those ports. Most firewalls, including Internet Connection Firewall in Windows XP, block NetBIOS by default.