I also got to demo Academy (Priestess vs. Warlock) and was pleasantly surprised. No zones / movement to worry about, and playing much like Arena otherwise, I think that it is designed well as an introduction to the larger game.
My primary concern with it revolves around the extreme usefulness of Attack spells. Also, it feels as if most or all of the Mages will be built fairly similarly... having Creatures really helps in Academy. I don't think you are going to be talking about the solo beater or even few "big" in that game; it more or less feels like everyone plays nearly the same Mage, just with different flavor text (more or less).
I think I still would prefer doing demos the way I do them now (via the six-zone PDF file method)... and think that Academy would only be used to demo the game in cases where the prospective player is younger or perhaps a heavy MtG (or other) card gamer.
