This is a typical sitcom, that had an Ok first series and a pretty good second series. There is nothing really new here, and for those looking to be shocked, a la Little Britain's second series upping the ante of "bitty", you may be disappointed. It isn't flash or toilet humour... you will never wince or cringe at what is being done or said, and it that respect functions like an old time sitcom.
The characters are very sitcomish in that they are playing obvious roles and have no semblance of realism. For example, Rowen Attkinson and his grilfriend act very similar to Al and Peggy Bundy from "Married With Children" with regards to the bedroom. Not inventive, but staying to a tride and true formula that guarantees laughs if you dot your 'i's and cross your 't's, which this does successfully.
Yet, personally, I was sucked in and enjoyed it, particularly the head of CID who, like JJ's "Dyn-o-mite", has a catch-phrase of "fannying about" which rears its head as more and more as the series goes on, which you will either love or hate.
If you prefer the growing trend and idea of comedy, that the charcters in humourous situations is funnier rather than gags and jokes, then this is not the show for you. For example, P.C. Goody's apparent homosexuality as well as his affinity for W.P.C. Habib, a voluptuous woman, is the basis of many gags and jokes.
Yet, taken for what it is, and not necessarily comparing it to much better shows, it is a simple and entertaining "old school" sitcom, that packs some fun lines and witty moments on par with Blackadder, only they are fewer and further between.