We've recently watched them all and enjoyed it on the whole.
Personally I preferred it when they were shorter stories, rather than one plot over the whole series. Sometimes the tiny band of police breaking up international trafficking and terrorism streched credibility a bit far, for me. Still a solid 7/10 though.
A lighter detective series we've been enjoying (and also just finished) is Brokenwood (UKTV Play). A bit like Midsomer in New Zealand but I like the fact they have a lot of characters who turn up in most episodes & feel this adds a bit of warmth and means there's more character development outside of the 2/3 detectives.