Tonight, CBS airs the final CSI featuring William Petersen. (The show is currently pegged for 9:15 p.m. Eastern, though that's soft, based on the running time of President Bush's farewell address and the attendant coverage — so be sure to consider that in the setting of your DVR, where applicable.)
Having seen the episode, I can tell you that Petersen's send-off contains elements of send-offs past from other shows (you'll know them when you see them), as Gil Grissom's departure shares space with the permanent installation of Laurence Fishburne's Dr. Raymond Langston, the new lead. Honestly, Fishburne doesn't seem to be moving entirely comfortably in the character quite yet, but taking an extremely high-profile position in an ensemble that's been together since 2000 can't be easy, even for an actor of his caliber.
Some shows manage what seem to be crippling departures surprisingly well: M*A*S*H, of course, did it a few times; ER gradually lost its entire original cast and survived commercially if not artistically; Cheers lasted long after Shelley Long bailed on the enterprise. Here's the question: What departures have worked the best? Maybe it's a big one, like when Clooney left ER, but maybe there's a small character whose absence was wisely leveraged into a great story. As television's top-rated show loses its lead, I ask you: what TV departures did you most admire?