I enjoyed the show. It has good storylines. Interesting plots that are engaging and some well placed comic relief. The island life is always the most beautiful character on the show and if nothing else you can watch just for the scenery.
I was annoyed with the consistent cast shift after falling in love with characters for a couple of seasons. The latest season with DS Madeleine is quite dull. Her personality is lackluster, how she dresses is like watching an older conservative maiden sister. I like that her hair styles are ethnic but that's it. Bring back Sara Martins! She was great as the first DS in the series. Real fiery, vivacious and awe-inspiring to watch. Beautiful actress.
The new DI, sorry I only saw one episode with him so I don't know his character name, seems to have him as a hypochondriac as his personality flaw and it feels forced and disingenuous. I'm open to having my mind changed so I will watch a couple more episodes of season 9.
I loved the series. I love the fourth character, the backdrop of island living, island life and it's inhabitants. It's probably the main reason I continued after the changes.
Despite all that I said, I would recommend the show. You decide how you will enjoy it.