I have to agree with the reviewer B.A.Vine on at least two counts --
The character of Sheldon Hawkes (played by Harper Hill) is not really successful. As you watch him, you're really aware of watching an actor playing the part - all very dramatic and full of overdone expressions. For the most part, the other characters have become believable and you're not really aware of them being actors, but Hill is just too obvious and unsophisticated.
Also, the storylines in this season aren't as gripping and the threads are less than enthralling. I suppose the benchmark for story arcs in the CSI set has to be the 'miniature killer' in the original CSI series. The arcs here in this season of CSI-NY just don't measure up. The whole compass-killer thing is OK, but in an attempt to create the mental state of the schizophrenic killer, the presentation is just far too tricksy and lets you into the 'secret' far too soon. This has the effect of engendering within you a feeling of some sympathy and with that, a lot of the tension evaporates.
The closed-room, da-Vinci Code episode (death house) has an air of such preposterous unbelievability that this erodes tension ... and as for how the girl who is saved from the hidden tank of water actually got into the tank - that little detail is ignored totally. It's all very false and smacks of a writing team becoming just a tad too self-indulgent.
Maybe I've just seen too many of these programmes, but I have to admit to a measure of dissatisfaction with season 6. It's good (in parts) but definitely not as good as previous seasons.