Today is the day. October 15th 2003. Microsoft announced the pending service lockdown nearly 2 months ago. Since then we've seen Yahoo rapidly follow Microsoft lead and lock down their own network.
Sometime within the next 24 hours Microsoft will finish their protocol upgrade. From feedback from the makers of Handheld PC IM client HPC:Factor is expecting all Messenger clients that run on the H/PC to fail.

Check back for more info as we get it.