Get it now from http://messenger.msn.com

New features:

• New login user interface and infrastructure (using IDCRL)
• Improved audio conversation
• Vodafone Interop (only in some markets)
• Voice Clip - send audio recordings to other users of MSN Messenger 7.5
• msnim: protocol handler
• Dynamic Backgrounds in the conversation window (using flash)
• Pre-Installed Themes
• New connectivity troubleshooter
• Expanded security settings
• New audio video setup
• Patching improvements - now the updates are very small
• Setup changes - note that this version of messenger can be installed on Windows XP and greater.
• Various bug fixes and usability improvements

Leah has a lot more details about this new release.