Not only have you been hearing about it for years; it's also been released for years: F# 1.0 came out in 2006! The only difference here is that with the release of F# 2.0, it's now shipped by the Microsoft "product" teams instead of "research" teams: it's included in Visual Studio 2010 available in boxes on shelves, whereas previously it was available for download.
Which is actually a pretty big deal because it means the integration into VS will be greatly improved. I've not tried the VS 2010 F#, but the plugin version was pretty clunky within the IDE.
It's a big deal because now you can just go ahead and use it and no manager can complain that it's not an official language. Hackers sometimes forget how conservative the mainstream IT industry can be.
Yeah, I was pretty sure that I played with it when I was doing .NET in school... Thought I was going crazy.
Nope you weren't going crazy, you were just reading The Register.
It's a kneejerk anti-MS site where all headlines must sufficiently glib before being accepted for publication. Blech.
There is a bit more to it than that. There's now a promise to no longer keep breaking binary compatibility. This part is an especially big deal.