Windows Live Messenger has just been moved to 8.1 Beta testing stage already. Microsoft has begun sending invitations to previous beta testers and I too have received an invitation to test out the new beta version.
From what i've read on their website, there is only minor changes made to the existing live messenger 8.0, so you chaps don't need to worry too much about the new v8.1 messenger.
What's New?
Roaming Identity - Your display name follows you any place you sign into. Now your display picture and personal message will follow you too. If you would prefer they stayed in place you can turn this off (Tools->Options->General -> Sign In -> "Use the same display picture....")
Contact Card - The contact card has gotten a updated look. Instead of a flip it does a slide to toggle between the Spaces and Contact information. Also no more squinting at an icon and trying to figure out what it means the actions on the card are now listed out plain and simple.

Emoticons, Winks, Backgrounds, Display Pictures - The menus have gotten an updated look. They include a recently used list and easy access to featured content so you can get new emoticons, winks, background and display pictures to use. hint: typcially in the featured section the first 4 are free.

SMS Phone Book - You now have a quick way to send SMS to a phone number or add phone numbers for your contacts. Just click the cell phone icon in them main window for a good time.

New Contact Emotion - In 8.0 all our icons got an update but we forgot a very important one. The contact emoticon. Type (M) to send it.

Status Menu includes Sign Out - We noticed people look in the status menu to sign out and so ta-da now you can sign out from the status menu.

Report abuse - Here is something you will hopefully never need to use, but it is there just in case.

Vista Presentation Mode - When you are in Presentation Mode on Vista Messenger will change your status to busy so you can avoid the embarrassing situation of everyone reading your IMs! Don't worry if you want to show Messenger in your presentation you can turn this off (Tools->Options-> Personal-> My Status -> Show me as "Busy"...).
*Anything else I should know? Yes. Vista users please follow the work around below to avoid the "DEP flash crash".
1. Uninstall Flash Player (Click Start->Control Panel->Uninstall a Program, then select Flash Player)
2. Close Windows Live Messenger and any other programs that use Flash
3. Open Adobe public Flash Player beta site
4. Click "Download Installer for Windows Active X" to install