Bundled as part of Microsoft Office 2011 for Mac's new beta, the latest build released to official testers has several bug fixes and sports the Windows Live color scheme while maintaining its OS X style interface, as the screenshots reveal:

The new design is now closer to its Windows equivalent
We at Messenger Stuff could not sign into the build due to technical difficulties, but those of you wishing to download the latest build can do so over at Wikikou.
Source: Wikikou: Mac Messenger 8 BETA 5 with Mac Office 2011Unfortunately I can never seem to log into Messenger for Mac and this build is no different, so I can't really provide a hands-on. Microsoft have stated that some features, such as file transfers and audio and video chatting appear to have several current limitations within the beta.
Download Messenger for Mac 8 beta
So what's up with Messenger? One of the most frequent questions we get here on Mojo and in forums is that you – our customers and community- want an update on timing for A/V support in the Messenger personal service, especially since we shared our plan to deliver a beta of personal A/V in 2009. Here's the update: progress has been slower than expected due to the challenge of connecting to the most current A/V code running on the Windows Live servers. We will not have a beta available in 2009, but we are close: we are in "dogfood", and we plan to have the beta available to you by next March. We know how anxious you are to use this new version, but I want to ensure we are delivering a top quality experience before we ship, and we will have that in March.
It appears technical difficulties have delayed the overdue feature of audio and video conversations, something we witnessed in working condition last march when an internal build leaked. Nevertheless a beta is expected this March and as a Mac user myself it cannot come soon enough.
Source: Mac Mojo: 2009 in review

Personally, I think this skin several flaws as it places too much emphasis on Leopard's style wallpaper, rather than the clean, slate feel of other Apple products e.g. iTunes. What makes this interesting is that others don't seem to agree and it has become one of the most popular skins created for MSN/ Windows Live Messenger. The skin has had over 1 million downloads despite still being in its beta stage.
If this skin looks appealing to you, then I recommend giving it ago as it is one of the fastest growing skins I've seen in terms of popularity for MSN/ Windows Live Messenger and its creator, coolzee deserves great credit for that achievement.
Download Snow Leopard skin for Windows Live Messenger 2009 (requires Messenger Plus! Live)Build 8.0.0.090205 has been circulating around the web, and offers audio and video support. This feature has been long-waited, but in the leaked build, the short-comings of the program make it highly unstable and not worth the download for these highly desired set of features. This is an early build, and a lot of work is still required.
Ever since Macs went Intel based, their potential has become wider. It appears that Microsoft may make Messenger for Mac 8 an Intel only build, a common trend among many pieces of Mac software. The transition period to Intel based Macs should mean the minimal amount of users are affected by this change. This however, is still unconfirmed by Microsoft.
Microsoft Messenger for Mac is shaping up to be a feature packed, highly-polished product. Although nothing can compete with the customization options within Windows Live Messenger for Windows, the program is intentionally designed to be simple; the cooperate mode shows it is not just meant to chat to friends, it is designed to enable productivity. When the complete version is released, expect an in-depth feature on all the individual changes.
View more information and a selection of screenshots
View the Microsoft product page for Messenger for Mac
I'm glad to say that the upcoming release of Windows Live Messenger, currently in beta, delivers the new A/V protocol that enables us to deliver A/V support in Messenger for Mac. It is cross-platform compatible and will work with Windows Live Messenger. This is a huge milestone that will enable us to continue moving forward with Messenger for Mac development.
We are very excited to be able to bring A/V support to the personal service. Our plan is to deliver a beta version of A/V in 2009. We are also working on additional features in both the personal and corporate service of Messenger for Mac for the next version of Messenger. We'll provide more updates and details in a future blog post.
Since we can't wait and are dying to share with you the progress we've made so far, at Macworld we hope to have a live demo of the A/V work we have completed to date in the personal service of Messenger for Mac. So please come on by the MacBU booth at Macworld!
This is some great news. As a new Mac owner myself, I do find the lack of features frustrating as times, and often boot camp my way into Windows Live Messenger. When Macworld comes this year (without Apple's presence) you will hear the updates as they come in.
Source: An Update on Messenger for Mac - Mac Mojo
Messenger for Mac 7.0.1 improves support for users of the VoiceOver feature in Mac OS X, and it fixes user interface issues that appear when Messenger is used with some European languages.
Download Messenger for Mac 7.0.1 (official source)
Find out more about Messenger for MacThe main improvement is the much-awaited introduction of audio and video chats, although if you're a non-business user of Messenger for Mac you will probably be disappointed. The A/V features require your network to be running Office Communications Server, but chats can be made to people on other networks using OCS and even to Windows users running Office Communicator. Business users also get updates to make Messenger for Mac more like Office Communicator, for example more presence information.
Regular users of Messenger for Mac, who use their Windows Live IDs to sign in, will see no sign of these new features. Instead, the main thing they have to look forward to in the new version is being able to give contacts nicknames and to search through contacts in a way similar to the 'word-wheel' in Windows Live Messenger for PCs. Another new addition is integration of the Mac OS X Bonjour technology.
The audio and video features for non-corporate users seem no closer either:
"We provided a look at our roadmap late last year and we remain on track--delivering A/V support to our corporate users and continuing to work with the Windows Live team to make A/V support available for (consumers)," senior marketing manager Amanda Lefebvre said in a statement.
Download Messenger for Mac 7 (official source)
Find out more about Messenger for Mac
Release announcement at the Office for Mac team blog
Find out more about the new A/V features (and the lack of them)
Get help for the new version
Information about corporate use and deploymentMS will no longer update the MSN Messenger for Mac, but they are going to release a brand new client for Mac OS X that is according to him 'Really, really cool and awesome' but he would not provide any more details due to his NDA.
According to the Mac BU [Business Unit] they've reached a milestone in the development process of Messenger for Mac 7.0 with the recent launch of a private beta with new Audio and Visual capabilities for a select group of enterprise customers using Office Communication Server 2007.
Some photos has been circulating around the Internet of the new program on display, which you can view here. All I can say is it looks very cool and I'm looking forward to the official release.
View the photos at Flickr
View Mac Mojo's post about developmentMS will no longer update the MSN Messenger for Mac, but they are going to release a brand new client for Mac OS X that is according to him 'Really, really cool and awesome' but he would not provide any more details due to his NDA.
Microsoft then responded to this well received piece of news. This was summed up by ZDNet:
As it turns out Office 2008 for Mac will include Messenger for Mac 6.0 [out of] the box [...]
According to the Mac BU [Business Unit] they've reached a milestone in the development process of Messenger for Mac 7.0 with the recent launch of a private beta with new Audio and Visual capabilities for a select group of enterprise customers using Office Communication Server 2007.
So MSN Messenger for Mac won't be re-branded, but it will get a lot of new exciting features to attract a wider market.
Messenger Stuff