This truly is something I'd long since forgotten about a long while back - ADS 1.1 has been in Beta for quite some time, so it's good to see that it was released a couple of weeks ago on microsoft.com. Although I haven't spent a great deal of time looking at ADS specifically, it is necessary for Virtual Server migrations using the Virtual Server Migration Toolkit, which was a seperate download. VSMT is now bundled with ADS in a single download.
Apart from the obvious bug fixes and the like, one of the main new features of ADS 1.1 is the ability to deploy x64 servers.
I used ADS1.1 and VSMT to virtualize a SBS2003 box earlier in the week. Worked a treat.