I went with C+. I found a lot of the cases really dull and at times could barely be bothered watching.
There were highlights, but I didn't enjoy the Stella story arc, which dragged on far too long. Even when Sid finally had a big moment it turned out to be all about Stella. I also didn't like Lindsay's storyline about her friends being murdered, it was pretty boring. Also, I find Peyton to be the most annoying character on the show by a long way. I think it's mostly her accent, why do all the English people on CSI: NY have to talk like that. I've lived in Britain all my life and no one I know speaks that way.
The Shane storyline was really great though, I'd have liked that to go on longer, maybe like the miniature killer or something. There was some very good writing in those episodes.
Although the finale was a very good episode, I didn't like the Danny/Lindsay bits, and their story the whole way through the series kind of got on my nerves.
That said, I have high hopes for next season. All the CSI shows have had poor seasons at some point and I'm hoping this will be NY's.