It also gets larger with a +1/+1 counter
Under the "old" rules, you did not die until the end of the current phase (regardless of your life total), so you could Contract all day long even at zero life and simply cast a game-ending Drain Life to decimate your opponent
You may exile no more cards than are required to pay the spells cost You do not gain mana by exiling cards for Delve, you exile cards instead of spending mana from your mana pool
Subsequently, Rev is better placed within existing theft-focused decks, such as those helmed by Gonti, Canny Acquisitor
now, Zendikar Rising offers a lot more options for spiffing up our decks
I offered to serve a mirror with his images up, and did with Aenyr (one of three really nice practically finished sets, the others being Dreamscape and Ankheret)