I like the Penguin and all, but I don’t think he’s a stand-up-and-cheer character announcement. We saw a version of this Batman: Arkham City video at E3 and the shrill English MC hooted and hollered (perhaps she was just overly excited about his incongruous cockney accent). At any rate, the inclusion of the Penguin doesn’t likely impact the core experience of Arkham City one way or another.
However, Rocksteady didn’t show us the whole trailer. Check out the electrifying conclusion below to see someone who will likely leave a a distinct impression on the Dark Knight: