The guys covering Pro Tour Philadelphia made an interesting point. The metagame shaped up very similar to what was being seen online before the event. This is unusual, as MTGO standard and paper standard are usually quite different. As one reason for this, combo decks have a real weakness in MTGO. Having to actually go infinite can be the death of certain types of combo decks online. In paper magic, you can just perform the combo five times and then say some impossibly large number. I sincerely wish they had posited a reason for this. Could it be that more competitive Magic players are getting into MTGO and qualifying for Pro Tour events that way, or was it just a fluke?
Another factor is the availability of cards and their prices. MTGO is always in flux and card prices stabilize very quickly. Card prices take a lot longer to stabilize in paper Magic because transactions take a whole lot longer, and cards cannot be moved between 5 different merchants in one minute. Keeping an eye on where MTGO prices are going on certain cards can be an excellent strategy for determining where card prices are headed in the near future, particularly if they are cards that fit into competitive decks. Availability is a large component to the appeal of MTGO. One can check the card prices of hundreds of merchants in a matter of minutes rather than hours. Also, access to any card you could ever want that is in print on MTGO are at your fingertips.