Mike Torres has the scoop in his blog post Windows Live betas - Writer, Messenger, Mail where he writes
Three applications I use on a daily basis just got updated today:
All three of them are rock-solid in terms of stability (of course,
they're still betas!) and come highly recommended by yours truly.
There are also a couple of blog posts on the various Windows Live team blogs about the betas. The Windows Live Hotmail team writes about the newly renamed "Windows Live Mail" in the post New beta software to access your Hotmail offline, the Windows Live Writer team has a blog post letting us know Windows Live Writer Beta 2 Now Available, and finally the Windows Live Messenger team runs down the changes in their latest release in the post Messenger 8.5 Beta1 released.
Like Mike I've been using the betas for a while and they are all rock solid. Check 'em out and let the product teams know what you think.