Catherine and Grissom are my favorite.
Yes, Grissom has a hearing disorder that passed genetically to him through his mother...she had it as well. There's not much they can do to fix it, so for now it's only a matter of time before he loses his hearing all the way. And none of the other CSI's know about it yet.
I don't know if any of you get TNN, but the other night they had a CSI rerun, and there was an ad talking about showing it from season one on.