Glad he's back. I was excited before the first movie came out to hear he'd be voicing Optimus. If for whatever reason it had turned out he wouldn't be returning chances are whoever was his replacement would have only wound up doing a very sad and horrible immitation of Cullens voice.
Plenty of folks. We're all entitled to our opinions, and some say they don't like Cullen as Optimus. Nothing wrong with that. I'm very interested in finding out how prevalent his character will be. As much as I'd like him to be front-and-center again, if it means giving the spotlight to other robot characters, I'd be okay with a decreased presence. Like, half of what he had in DotM.
Personally, I prefer Peter Cullen as Optimus Prime. Gary Chalk was great as Primal. I didn't care for his Prime in Armada or Energon, but I put that on the voice director not the actor. It took me a bit, but I actually grew to like David Kaye as Prime as well. I think a lot about the character comes from direction and script... not the actor.