The biggest hurdle is the addition of a multitude of new, highly specialized classes and skills. The books were designed for use with the 3.0 D&D rules, so you might be faced with the possibility of overhauling the CoC rules to include some of the concepts involved. Still, I liked the three I have read (Feds, Supernatural & the Mob).
I liked the premise and details about handling crime scenes -- but didn't like the plethora of new skills they used to implement them. Characters just wouldn't have enough skill points to ever make use of these things.
With some house-ruling you could fix that, but I'm waiting to see if any alternatives crop up.
There was something about Brits writing about US law enforcement that made me feel....funny inside.
I wasn't overly fond of the books--they seemed very vague and over-generalized.
That was several years ago, however, so I can only offer you impressions and feelings rather than being able to site specifics. If it says anything, I sold the books not long after buying / reading them.