Hi there! Not sure if you're new, but welcome!
Thus far in season six we have seen hints of our lovely geek couple being together. In the first episode, Grissom brought her a veggie burger for lunch. I thought it was a touching move on behalf of a boyfriend. Also in the first episode we had Sara gently teasing him about motive.
In the second episode, she teased him about his obsessive nature, and he teased her about their age difference. It's nice to see they are comfortable with it. When Ecklie tried to get the Geeks to disagree on something, Sara sided with Grissom, and Ecklie made a comment about how, "of course" she would. Sara and Grissom shared a look, asking each other in that look, "Does he know about our secret love affair?" Sara's next look says, she doesn't think so.
At the end of episode 2, Sara went to Grissom in his office, where he was obsessing about a case. She was worried about him, and checking on him. Of course, he brushed it off, but you could tell he was thinking it through, and you could tell she was worried about her man.
In the third episode, we got a little backstory, with Sara recounting the first time they met, and how she heard he was a dull speaker, but that you can't rely on a first blush. Grissom, still a little flustered from Sara thinking he was dull as a speaker, corrects her with what he said in the lecture, and they share a moment. Also, before this conversation, Grissom gave his woman a quick once over.
There's also an amusing moment in episode 3 with Sara coming at Grissom with a chainsaw. It was for the sake of an experiment, but his eyes bugged out of his head, and I think he made a mental note not to ever piss off his woman when she has a power tool in her hands.
Hope that helps, and welcome!