See, I thought Keppler was a great character and far from boring. He wasn't Grissom, but wasn't meant to be. He was his own character, and very interesting. I loved his flaws and his story. I am sorry he got killed off, because he could have made an interesting recurring character. With the way they did the storyline, I doubt he could have stayed a CSI even if he hadn't been killed.
I'm ambivalent about Sara leaving. She was never my favorite character, and at times could be unlikable due to her inflexibility and not being able to apologize very well, but that's the way she was supposed to be. However, I think they gave her the best exit they could have. They took the time to show how the kidnapping was eating at her and that she was on the verge of losing it completely. I definitely think the show lost something when she left, and I'm not sure how I feel about her returning. She left, and it's over.
Lady Heather was another great character. I loved the way she interacted with Grissom, especially in "Lady Heather's Box." I wish they could have explored that dynamic between them even more. Especially because no matter what Billy Petersen says, Grissom tapped that.
However, I will say this. They've played out her storyline. OK, she was back for "Pirates of the Third Reich," because of her daughter. In "The Good, The Bad, and the Dominatrix" Grissom went to her as a friend, nothing more.
So, I'm not exactly happy about her coming back. It just seems like overkill, them bringing everyone back from Grissom's past.
Too keep the thread on topic, I wish Grissom hadn't changed, either. He was cool and quirky, and sometime after the Hearing thing, he stopped being so quirky, and started being brooding. It cost him a lot, especially because I don't think his relationship with the team was ever quite the same afterwards, especially in season's six and seven.
I also wish that in New York, they hadn't lightened the show so much. Season 1 was the best season. There was a gritty darkness to the show that had nothing to do with the Blue Filter. It was quintessential New York City. Rats, Central Park, Bicycle Messengers, the Circus, etc. All of it gelled together in a very cool way. Now, they tend to focus on the glitzy elite of Manhattan only. I think they took something away from the show when they lightened the mood.
Some of it had to do with Aiden leaving, because the Brother/Sister dynamic between her and Danny, was cool. He was open to her in a way he has been with no one else, before or since.
Overall, though, I think that New York is not as good as it once was. I'd like to see them get back to that.