Seasons 1-2 are pretty fun dark thrillers. The formula gets a bit more of day time drama like BS in season 3-4 but remains pretty entertaining. By Season 5 it lost all of the original fun - only way to watch it is to fast forward all the melodramatic flashbacks - you can watch the season in 2-3 hours doing so and you will not loose a single thing of value from this season. Season 6 tries to track back to original ideas but I found Season 5 to be so insulting to the basic intelligence of viewers that I simply couldn't get in to it anymore.
This trend the studios have to kill the formula that made a show popular with cheap drama is really getting to be obnoxious.