While looking to install smbclient on my laptop this morning to talk to some devices on my home network, I was pointed at a security advisory regarding SMB2. It's about a known defect the SMB2 implementation on Windows 7 -- kind of interesting to have pre-release security defects publicised already. The FSFE's statement is here, and you can find English-language Heise coverage here.
The intermediate work-around -- isolate Windows machines from the Internet with a good firewall -- is good practice anyway. Do not let SMB traffic escape from your local network.