HomeLan have also posted a Q&A with Microsoft's Hal Milton about Mythica, their massively multiplayer RPG:
HomeLAN - How has Microsoft's experiences with the two Asheron's Call games helped with the development of Mythica?
Hal Milton - As with any endeavor, experience is more valuable than anything. AC and AC2 have given many folks at MS an understanding of not only the game play and community support necessary for giving players a great place to play, but also the more arcane ins and outs of the backend stuff players don't (or shouldn't) experience.
Being able to create a service that is transparently stable and secure for folks to have fun in takes a lot of trial and error. I believe that Microsoft's experiences with supporting AC and AC2 have helped us identify, catalog, and learn from the good, the bad, and the ugly of the online development world.