Issues addressed with this update include:

MP Lag seems to be fixed even for severe clock drift. The major MP lag issue was not related to network bandwidth.
The major issues with hosting behind a NAT have been fixed.
MP ratings are fixed. Ratings will be reset as the current ones are not meaningful.
CtW crash related to 16-bit vs 32-bit color on battle loading has been fixed.
GameSpy Arcade and the in-game matchmaking services are now compatible.
You can now check for updates without going into GameSpy.
Chat message are now white with only the player name colored.
Armageddon does not happen in "Sandbox" mode (1-player).
Additional anti-cheat protection.
Much better support for pre-prelease patch testing.
Fixed ping-sorting for in-game matchmaking.
Added a semi-documented way of adjusting the colors as requested by some colorblind players. Thanks to Ike for putting it in and providing a sample set of colors.