I heard about this yesterday, courtesy of a friend posting a link on Facebook. After watching the Youtube video and reading the Amazon reviews, I immediately placed an order for the CD, but due to the wonders of the internet, I've been listening to it all morning via Amazon's Cloud Player.
It reminds me very much of classic 1970s Steeleye Span, the overall sound is similar to albums like The Journey. It's also making me want to re-read the Tiffany Aching books, which in my view contain some of Pratchett's very best writing. His descriptions of the chalk country where Tiffany lives are so evocative. And they're funny, of course and there's a very good Nac Mac Feegle song on the album. :)