Second eye opening of the series belongs to Locke.
The first half of the first season dealt much more with basic survival and practical matters. How to find food, fresh water, shelter, and fend off wild animals.
Sayid's objections to burning the bodies is not very practical, and from the beginning he seems to be a practical character. I think the series was trying to paint him as a religious man, because of his objection to burning the bodies, and reminding Jack of religious issues, but it didn't go much more than that.
Watching tough-guy Sawyer fight with roly-poly Hurley is one of the funniest things in the show. Especially a couple seasons later when Hurley really gets the best of him.
Locke's first flashback is golden. I was even almost full again into thinking he was military. Terry O'Quinn has played many such rolls in his career, and is as natural as a military commander as office nerd. Or Starfleet Admiral for that matter. We also meet one of the first of the cross-characters, Randy, who shows up in Hurleys flashbacks.
Kate says she's a vegetarian. We'll just see about that.
The episode told us right up front that Locke did not have use of his legs, but we missed it. His story of the double amputee that climbed Everest was a perfectly normal story in his situation. We also get the line that defines Locke's character first here, "Don't tell me what I can't do."
Locke is the first character that the smoke monster reveals itself to. They will become intimately acquainted in the future. Well, Locke's body will.
We have our first Christian Shepherd sighting. This may be the weirdest thing of the series thus far, seeing a man in a suit standing on the beach by himself.
The reveal of Locke's paralysis in his flashback was jarring at the time. Obviously it loses some of its impact now, especially since the clues are now easily recognizable. But it's still amazing. Locke's since of the island and the smoke monster as redemptive and healing sets him on an early path much different than the other survivors.
Thoughts after four episodes:
1) No sign yet of Ethan even in the background actors. Nor do we see Frogurt or Arnst. None of these other survivors have been cast yet. And of course no Nikki or Paulo.
2) There is just a mess of amount of plane fuselage lying all over the beach. I don't remember seeing all that in later episodes at the beach. Is that explained? Or did I just overlook it?