As of April 4, 2014, more than 1000 petitions for inter partes review have been filed.  Since the first day, inter partes reviews have taken off with a steady stream of patent challenges:

How have these petitions been disposed of?  About 81% of them are still pending, 11% were not instituted, 4% settled after institution, and 4% have ended in final written decisions.

Of the 11% (108) Petitions that have not resulted in the institution of trial, 41% (44) were denied on the merits, 23% (25) were denied as time-barred, 31% (33) were settled, and 4% (4) were abandoned by the patent owner.