(Update 1-19-2011 after the following was posted: updated my site to use JAVA script and Facebook generated tags to implement the content in html rather than ASP .NET)
Well... I installed it, and followed the directions to use ASP .NET in my web to integrate some facebook functionality into my site. Locally, it works, when I try to put it on the server, it's a flop, and just displays the ASP code. I took some screens, both local and on the server. Things I had working locally: a facebook comments section on my contact page and a like button on my home page.
locally:
on my charter web space:
Aside from that - anything that I made in FrontPage 2002 is horribly incompatible with the new cshtml extension needed for these functions. I blame FrontPage's obsoleteness rather than WebMatrix, but transferring to WebMatrix totally wrecked my navigation bars from FrontPage, and it took a lot of repair before I got it back to usable condition with the new Facebook features (like button and comment portion)
At one point I had all of my links for index.htm changed to Default.cshtml, and my links for contact.htm changed to contact.cshtml... and then I accidentally opened FrontPage 2002 rather than my ftp client
... immediately, as soon as FrontPage opened (didn't click anything other than the close button) it changed all of the navigation links back to index.htm, for EVERY page
IMO: it may be worth it if you have web space that supports ASP .NET, but make sure first with the "publish" icon (second to top left) of WebMatrix. It will run compatibility tests. I'd recommend this tool for people starting a new web page from scratch.