CBR just posted an article covering Activision's SDCC 2012 Transformers: Fall of Cybertron panel, which featured voice actors Peter Cullen, Nolan North, and Gregg Berger. During the panel North mentions working with Cullen and Berger on both Transformers: Fall of Cybertron and Transformers Prime.
Berger spoke about voicing Grimlock, stating in the Dinobot's voice that he was "driven by aggression!" Without any filters to get in the way, Grimlock's strength has a great capacity, even if it's slightly out of his control. Berger thought it was incredible role for an actor to play. He also did a little bit of "Me king!" in Grimlock voice, much to the delight of the crowd, while explaining what a great ally he was to the Autobots team.
North, the iconic voice of Nathan Drake from the "Uncharted" games, explained how much fun it was voicing both Autobot (Cliffjumper) and Decepticon (Bruticus), changing tones for each character. He jokingly poked at Berger in his Bruticus voice, similar to his Grimlock role. He also felt honored to watch Berger and Cullen work, both on this project and the animated "Transformers Prime" series.