The blog post includes remembrances from some of the crew of The Clone Wars.
A peek at his filmography on IMDB reveals that you hardly have be a Clone Wars viewer to have enjoyed this man's work. Among a multitude of other roles, he played Mister Pitt, Elaine's needy millionaire boss on several episodes of Seinfeld, John Hammond's butler in The Lost World: Jurassic Park, and the bearded wise man who sent Bruce Campbell to fetch the necronomicon in Army of Darkness (along with the poorly heeded instructions to speak three magic words).
Source: The Official Star Wars Blog
Army of Darkness DOES kick ass though.
Looking forward, I wonder who they'll get to replace him in the Clone Wars? Nick Jameson? Sam Witwer? Or maybe even Ian McDiarmid himself? Or perhaps they'll look for an unknown. I happen to do very good Palpatine, Sidious, and the Emperor voices.