Season 1-2 were amazing. A lot of unnecessary drama. Not sure why it took so long to reveal one particular issue. But it was a great story.
The nose dive started in the second half of season three and in season four they were completely submurged in the Atlantic with no hope of resurfacing or survival. It just shows how over dramatisation can destroy a good storyline.
The good stuff... season one is the best of them all, you could tell the writers were escited and ontop of their game. I also love how they broke the story down into seasons, and each had a different angle to it keeping the story fresh.
If only we could forget that season 4 ever happened.