It's been sooooo long since I saw this. It made me so happy to see it again, especially as an adult. Honestly, I think the last time I saw it must have been about ten years ago (discounting one drunken group viewing in the middle there somewhere).
This was the only one of the original trilogy that George Lucas both wrote and directed, and boy does it show. Lucas is a great ideas man, but I read once that the less he had to do with the original trilogy the better it got — and they were right. Episode IV (both written and directed by Lucas) is easily the simplest and least interesting of the three. V is the best and most complex because it was neither written nor directed by Lucas, and VI is great, but maybe not as great as V. Sure enough, Lucas co-wrote the script for VI. Fucking Ewoks.
So dialogue and direction-wise, episode IV is a bit pants, as steve has pointed out in his comment. But those things weren't what made this movie great. The vision George Lucas realized (and yes, he was a tremendous ideas man), the charisma of the lead cast, and the special effects are all what rope you in. And that's enough, to be honest. Most movies would be lucky to have those things.
I don't want to rehash the obvious things, so I'll focus on the things that stood out for me on this ten kabillionth viewing. One is Obi-Wan Kenobi's demise. I'll be honest — I've never understood his line, "If you strike me down, I will become more powerful than you can possibly imagine." Does anyone know just what the hell he's talking about here? He might have meant that he could influence events far better as a ghost than as a living being (which he does in episode V), but couldn't he have done that alive too? Are there scenes we don't see where his ghost secretly sneaks into Darth Vader's bedroom and rearranges stuff behind his back to gaslight him, or what?
The thing I noticed for the first time is the irony in some of the dialogue. You just don't pick up on this kind of stuff as a kid, but it's in there. People have talked about the awkward love triangle between Leia, Luke, and Han Solo, but I think that only happens in episode V. Here in episode IV Solo doesn't give a flying fuck about Leia. He might have some attraction to her which later evolves into a fuller appreciation, but when he first meets her he clearly doesn't think much of her. The only reference to him liking her is when he realizes Luke likes her and he winds Luke up by saying, "Hey, you think a princess and a guy like me…?" Luke shuts him down and Solo laughs to himself, which I bloody love! He's not displaying an interest in Leia here, he's just teasing Luke.
So yeah, it's kind of nice to know that a movie I've seen so many times still has some surprises for me. I'm looking forward to moving on to episode V now.