I'm really enjoying the entire twelfth season so far, and this episode was just as strong (if not stronger) than the first six - although I did really love the season premiere. I really like both of the new characters and Morgan in particular shows new sides of her personality every episode.
Usually, I complain when episodes don't have enough Sara in, what with her being my favourite character, but recently I've been having that kind of experience with episodes without much Cath, because her time's so short. (And as an aside, on the subject of Cath, I've been re-watching season 1 and she's aged incredibly well.) But I'll agree with what others have said about there being some really good scenes with some of the characters such as Hodges, and I'll also echo the comment about Greg in a suit (drool).
As far as the case goes, I'm tired and have a lot on my mind right now so I did get pretty confused towards the end, but I did think it was an interesting one - and I love any kind of gruesome scenes/images in CSI, so I got plenty of that. I reckon the knowing straight away who the killer is is just something that happens when you know the show really well, because you get so much into the mindset of the way the writers think. Occupational hazard of watching too many repeats while eating dinner, I guess.
Overall, no significant complaints, although I'll juyst throw this out there (not necessarily as a bad thing, just an observation): have we ever heard as much about the personal life of any one character during their entire time on the show than we have about DB during his first seven episodes?