There goes the show...
I've always loved CSI primarily because of Grissoms character. To me, he and his idiosyncrasies are what made the show worth watching. I've always considered him the ideal counterbalance for the characters of rest of the team, possessing many of what I'd consider the ideal character traits for a CSI.
I really admired his ability to be objective and unbiased even in the face of incredibly difficult situations. Yes, he was perhaps the biggest geek in the entire cast, but that is what made him so special.
His ability to make true, valid connections through logical deduction, where others were often too emotionally driven or too willing to rely on their hunches or misleading past experiences for guidance has always been an inspiration.
Gil Grissom will be a great loss to the series. I honestly can't imagine CSI without him, and i seriously doubt they will be able to craft a character good enough to fill the shoes he will leave behind...