I'll add my 2 cents here...
First of all, I agree with everyone's assesment of Catherine so far. The main thing is she isn't ashamed of her past. I think it adds to her character and it brings something to her work the other's don't nessicarily have; Life Experience.
Althoght this is not meant to be a comparison by any means but Catherine can and does deal with people better than Grissom and the other lead woman, Sara.
She also owns her sexuality which also makes her a strong confident woman. She knows how to deal with men and she isn't afraid to take them down a peg or two, including Grissom. Example :
Slaves of Las Vegas and the converastion between her and Lady Heather about death being a mans world and she acknowledges that men shove around their weight all day (I can't remember the quote exactly, but it's something to that effect
)
As for men, she sometimes does wear her heart on her sleeve and I think she surprises even herself how vunerable she can be. Case
Viva Las Vegas when she caught Chris cheating on her, she was visably upset and I think that wasn't the recation she thought she would have.
As for Keppler, she saw something good in him when no one else did. That's part of her personality, she's good a reading people and she saw that he eventually would 'land on the side of good' as she told Grissom.
I'm not sure if she is the antithesis of Grissom since they both can fling sarcastic remarks but she is different from him. She is more outgoing and like I said, deals with people differently. While Grissom is more introverted and keeps his emotions to himself, she is obviously more vocal on lots things and tries to help him do the same. That is part of what makes her and Grissom so effective in leading the team. She brings something he doesn't and vise-versa.
I think that is all for now, I'm sure I'll find some more attributes I love about Catherine Willows.