This game ROCKS. We were under an NDA which prevented us from discussing it previously, but it is as bad or worse on your time as real magic is (or was for those starting to burn out). Whenever you want to play a game, you can get one. Whenever you want to Draft, you can get one. You wanna play a sealed game at 1am, no problem, someone else will be there.
To the questions on "sneaking" cards in, at this point I think they have a pretty good system. The card database is checked when you log on, and also in tournaments, your deck is checked at the beginning of each match for legality. Your current deck is even kept at their site for league games.
There is Multiplayer including Attack Left(3-6, last man standing), 2-H Giant, 3-H Giant, and Emporer.
Drawbacks: Not all of the current cards are implemented yet (about 40 OD cards, 5 invasion cards, and a couple AP cards), Legacy sets will NOT be implemented, it is only the current standard and from what I hear old sets will be eliminated as they do in CM (Cardboard Magic, hehe), chess clock(long lenghthy topic on this stalling prevention mechanism).
But by far the positives outweigh the negatives on this product. The key thing to the success of this product will be the pricing. they haven't announced it yet, but I feel it can make or break this awesome game.