So I heard something second hand the other day, take it as lightly and with as many grains of salt as needed.
A former MS programmer works a floor above me. Used to be on the network filesystem team. I guess MS hasn't touched the TCP/IP stack since NT3.51 with the exception of some random hooks to tie stuff like RPC and PnP to. This is an inherent security risk, as the firewall code which Windows uses attaches to these hooks, which forces the entire stack to be completely up
before the firewall code can start. This means the average computer is unprotected for 30-60 seconds on boot, more than enough time during a virus outbreak. Well, I guess MS finally decided to rework the stack to better integrate the firewall and other stuff, and removed lots of these so-called hooks. Same hooks Windows used, and thus the same hooks many, many network-based programs use, hence the delayed official public release of it (to allow businesses to rewrite network stuff, if needed and offer patches).
I'm not going to begin the testing process on any of my or my clients' machines until at least two weeks after it hits winupdate for everyone.
In the meantime, 2.4.27 was released and I'm staying busy with that.