Let's break it down into 3 parts.
1. The beach: The weakest of the three. I enjoyed the Jin/Sun scenes(especially the scene where Jin confronts Charlotte).But it still felt somewhat dragged out. However, the surgery was surprisingly well done. I liked the drama there, even though we all knew Jack wouldn't die. That's where the main issue of this episode is. We know Jack doesn't die! Had this been before his flashforward, it would've been suspensful. But this way, it was... weightless. Also, I thought the writers might use Jack's illness to have some huge conflict on the beach that would require Jack's leadership -- no. It didn't happen. SHAME!!! At least... I thought that would've been great.
2. Claire/Sawyer/Miles: Oh, I smell a winner right here. This was really exciting. I grew to like Miles alot more. I don't know why, I just did. And finally, we found out Rousseau is dead! I'm sorry, but I just can't believe how everyone doubted that. I went on several forums creating theories/reviews where I mentioned she's dead -- everyone told me I'm stupid, she's not. Anyway, that scene where Miles "experiences" the shoot out -Interesting. I just hope we'll get some kind of explaination, and it's not just something we should accept without anything to back it up. I liked Sawyer once again. I can't believe it actually happened: he's a caring person. But the main event is Claire running off.... with Christian? What the heck? That was creepy. And that just kind of confirms my theory from last episode that she'll end up in the cabin with Ben and John.
3. The flashforward: Great. Started somewhat slow, but in the end it was really great. Showing Jack's breakdown was done well. It was very subtle, and I think considering the circumstances, realistic. But how the hell did they get off the island? And at what price? I really don't think it's just 6 people flying off on a helicopter, then cruising away on a huge ship. Everyone seems so traumatized about it. I'm starting to feel that the writers are smart saving this for the finale. Hurley's(or Charlie's) prophecy was goosebump worthy. So apparently Jack can't raise Aaron. And Hurley knew Christian would visit him! Aaaah, what's going on? Is this even real? I'm not a particular fan of Jack/Kate but this episode really made me feel for them. I think big part of why this episode was good is due to Matthew Fox's amazing acting. And Evangeline was awesome too.Of course hanging around half undressed is always a plus point... hehe. Anyway, the flashforward was very emotional, and well done.