I watched the show last night. I usually find the serial killer episodes chilling and very creepy.
Of course, I was also preoccupied with the fact that the episode was Gris' last.
I will miss him for sure. The show won't be the same without him. That said, I am looking forward to the changes the show has in store; curious to see how the new guy works with the team.
I thought the ending with Sara was dramatic but sweet. I think Gris would be happy in the jungle with thousands of bugs to study ... and if that life is with Sara, then so be it.
And like you said, the show will survive (at least I hope it does)... there are thousands of seasoned CSI-ers out there who will surely keep watching.