It's out on Steam at $4.99. Offers five new decks and more campaign levels.
How is the base game? I was going to pick it up last night but Steam was slowed to a crawl (because of Borderlands, I'm guessing).
The engine's nice and relaxing to use (doesn't lock down sound cards which means I can play my own soundtrack). The biggest downside is that you cannot build your own deck; the decks are well-made, but you can only tinker with the cards in the deck. Replay value's okay and the expansion really helps with that. The algorithms used in shuffling decks become predictable after a while (land draws for five turns and so on), but the highest difficulty setting makes the AI vicious and those matches are challenging.
Cool! I played the first one on 360 and liked it, but I just couldn't get used to the controls. I figure this is definitely a game that would be better with the keyboard/ mouse setup.
In the options menu, single player auto-progression can be locked and your computer opponent will wait for you to confirm any spell they cast (doesn't apply for creature, enchantment, or artifact abilities).
I haven't used any of the expansion decks yet, but so far my favorite is Jace's deck-destroying deck.