I'll give it a B.
I liked how this season we got a few 'serious', gritty episodes such as 'Commuted Sentences', 'Child's Play' and 'Admissions' which all dealt with serious crimes and heavy issues.
I liked the start of and the end of the 333 storyline. I loved The Thing About Heroes for the insight into Mac's past, seeing Mac go to Chicago, and seeing the team try to solve the case in NYC while he was away. Drew was a blatantly obvious choice for the stalker though. They'd have done better to have Drew pop up out of nowhere in The Thing About Heroes, because his motive for wanting revenge on Mac was interesting, and not cliched - it wasn't someone from an old case. But having Drew go after Stella, and turn up in most of the eps where Mac got a phone call just made it too easy.
I loved the Ruben storyline, and Danny's guilt, and the Danny/Rikki interaction. It was tainted by the inclusion of D/L though. I loved Flack going to save Danny's ass in All in the Family.
I liked that Adam got more screen time, especially in eps like Down the Rabbit Hole where we got to see him in all his geeky glory.
The technology stuff (SL, the Bond episode) was fun, but I can take it or leave it. I'd rather have darker storylines and more complex and diverse vics and criminals.
I liked the Halloween episode, it was fun.
Not enough Hawkes or Flack this season.
I loved the return of Reed, Gerrard, and Sinclair, all are great characters. I liked how Sinclair and Gerrard were shown to be human, with a decent side and with flaws. I loved the interaction between Mac and Gerrard in Admissions, particularly the end scene when Gerrard shot the pedophile. I'd love to see that followed up next season.
I liked RND for a Stella ep, but not the Drew thing because it was just her being used by a creep again.
Not enough diversity - the majority of crimes seemed to be committed by white people, and they were mostly wealthy white people. Jeez, can't a homeless person be killed or kill someone? And also, the reasons for the murders often seemed petty. I'd like to see some deeper motives for the killers, like in Commuted Sentences or Child's Play. I know people kill each other for petty reasons, but they also kill them for deeper, more serious reasons too.
The Cabbie Killer case was great, until they made the killer a religious nut. A cold blooded killer who killed for no reason would have been more intersting.
I liked the character interactions - Mac/Sid, Mac/Adam, Stella/Adam, Mac/Stella, Flack/Danny (loved them at the game at the start of Personal Foul, and Flack being there for Danny in AITF), Hawkes/Lindsay.