Well, as was said in a thread over at HobbyTalk, he lived a very full life, with one hell of an impressive body of work. "The Day The Earth Stood Still" is one of my all-time favorite classic sci-fi films, and I was so glad that we was able to do the clean-up work on "ST:TMP" before he died. Although I suspect there was still more he'd like to have been able to do to it, the new cut is a really wonderful reinventing of a great film, another of my all-time favorites.
Rest in peace, Robert! We will miss you, but you will live on through your amazing contribution to our popular culture. Thanks for everything!
He also directed The Sand Pebbles with Steve McQueen, one of my favorites, as well as editing Citizen Kane, and host of other classic films. And don't forget the musicals. There's a nice write up on the Star Trek site.