Sorin has seen some play, actually. Most recently, he showed up as a singleton in a Grixis control deck that Top 8'd the Starcity Games 5k in Los Angeles last weekend. (The deck ran one of him over a fourth Ultimatum.) Other Grixis control decks have been doing the same thing. (Source) Sorin is an absolute house if you can land him--he can easily win the game for you once he comes out. (And he's obviously brutal in EDH.) Read the decklist... it's interesting. Not sure how I feel about the courier's capsules, especially when he could get another divination or a Jace instead for LESS overall mana. But hey, he Top 8'd the 5k, so who am I to talk? *cough*lucksack*cough* In EDH however, he is brutal. As are many other cards you wouldn't run in a "conventional" constructed deck. Which is why it's an awesome format. :-)