Here, Dungeonscape talks about starting the beta. It's coming!
http://www.dnddungeonscape.com/dungeonscape-beta-lets/
Edit: Invariably, people will come here to ask when it starts without reading the blog, because, internet. Here are some quotes. Make of them what you will.
We will begin sending out invitations for the WEB BETA starting next week!!
I did not read your post. So...when does the beta start. Just kidding. 
I'm looking forward to seeing this. I like the idea of tools like this more than I like physical books.
MrHotter wrote:
Good news indeed! I cant wait!! 
Here is the Angry DM review I was referring to. I'm impressed that he's impressed! And from everything I've read it seems Chris Matney is by far the man for the job.
I'm excited by this. I got to use it at Gencon and came away very impressed with what they had and what they stated they wanted to have. The interface was pretty easy to use, character creation was very quick, and the ease of getting rule information from it was wonderful. I loved the notion that they want to have a communication ability with it to where a DM with dungeonscape can send messages or information to a player that has it running as well.