Saw this Monday night at an advance screening.
EDIT: Spoiler cut lifted now that it's in theaters.
Yay! Overall, it was a good movie! It was very true to the adventure and "swashbuckling" spirit of the earlier films. But the biggest surprise was how well Harrison Ford looked! You aren't always thinking about how old he is, he is just Indiana Jones the way you remember him.
There are a couple of funny references to the fact that everyone is older, and some very welcome nods to the other movies (especially Raiders). Cate Blanchett is fantastic as the villianess.
The action scenes are done pretty well. They were my favorite part of the older movies - the fact that it was real people doing things, not cgi, and that's how it is for the majority of Crystal Skull.
I only have two nitpicks. The first is don't look to hard at the timeline. Just accept things and move on, because certain bits don't hold up to scrutiny. Second, Steven Spielberg is a creative genius. His imagination is what created Indiana Jones to begin with, but even geniuses need to be reined in once in a while. There are two scenes specifically that start out so well and are amazing, but then he takes it one step too far, into preposterousness. He needs to learn how to just let a good scene be good, not try to take it over the edge all the time.
Definitely worth seeing, but my allegiance still lies with Raiders.
I just rewatched Raiders last night. Seeing it again after Crystal Skull, I can't believe the number of references and film geek nods to Raiders that KotCS has!