This could very possibly be the best movie of all 6. And that's coming from someone who is a huge Empire Strikes Back fan, who thought the first 2 were something that shouldn't really have had the SW name on them. They were good themselves, but not quite what was to be expected. Revenge of the Sith. Wow.
The effects were incredible. ILM really stepped it up for this one. The battles are incredible to watch. There's so much going on. During one of the lightsaber battles, you can watch the war outside and see ships being blown up. The sound was also what is expected from Lucas.
The acting was good. Some scenes felt forced and I could have done without. There are a few lines that make you laugh. And not because they're jokes. Because they were delivered terribly. Vader/Anakin especially.
The story was exactly what it had to be. A tie in from Clone Wars to A New Hope. And the story is great. It could have used a little more development in turning Anakin, but at 2 and a half hours already, I see why George cut it back. I never got bored, there was almost always something interesting happening. The fight between Obi Wan and Anakin was absolutely incredible. There was a small cheer from the crowd when Vader's mask came down and he took his first breath. (There's also a small glimpse of what he sees through the helmet. Very Cool.)
Overall, I'd say it's a 9. A little better acting, a little more development on Anakin, and it'd be perfect. If you like SW, you'll see it anyway. If you don't, go see it anyway. I know I'll be going back Saturday to see it.
BTW, Yoda proves once again that he is the most badass mother-eff'er in the universe.
Edit: One thing I want to add. As I was leaving the theater, I wasn't sure if I should be happy that the saga was complete, or sad that so much bad had to happen to get from Clone Wars to A New Hope. But now, a few hours later, it feels good to know that the story comes full circle and it's done now.