I would agree that seasons 4-6 are not as good as seasons 1-3, but I would not go as far as to say they "suck." Then again I'm not as quick to label things that are inferior to their predecessors as "sucking" as a lot of citizens of the internet are. They're still Lost and they're still great, and I also enjoyed the series finale very much. I've always compared Lost to a Stephen King epic (and on a side note he was a big fan of the show and the show runners were big fans of his). Great ensemble cast of interesting characters with well-developed back stories. An epic sci-fi fantasy story that's really about the human relationships and stories of the characters. Gets a little convoluted and silly toward the end, maybe not wrapped up in the best way possible, but when it's all said and done it's hard to say you didn't enjoy the work as a whole. That's my take anyway.