I revisited the previous three films before watching this one and found that they were much less interesting than I remembered, so take that into account. Because of this, I wasn't terribly let down by this movie, although it has it's flaws. First the good, though.
Great performances by all involved. Ford seemed to need a couple scenes before he felt like Indy, but got into his groove soon enough. The film acknowledged the character's age with good effect, though Ford still seemed to do a very surprising amount of his own stunts. (That or the face replacement was REALLY slick!)
Cate Blanchett was especially enjoyable as the stereotypical "communist Russian bad lady".
The film was served well by modern special effects and the sets were great in number and textured in design. Some great visual material.
On to the bad. As my wife pointed out, "no one ever seemed to really be in danger. It was like they were at an amusement park going on a bunch of fun rides." This is true. The logic of this film, even more so than previous Indy films was: If it's cute or funny, it doesn't have to be believable. Unfortunately, if you don't appreciate the "cute" or "fun" sense of humor in this movie, you'll just be frustrated at the obvious lack of realism. A refrigerator, a snake, some groundhogs, ants and a "tarzan" scene all come to mind. (You'll see what I mean.)
The film also departs from its supernatural roots to explore themes of science fiction. This is probably because of the time period the story is set in (indicated by an iconic image of Indy and a mushroom cloud early on) and didn't bother me much, but know going in that the concept driving the movie is different from the norm.
The movie is very aware that it is a sequel and often seems more interested in reminding us of previous films than in making a new one. It's not as overdone as it might have been, but it's enough to be slightly less than charming in the big picture.
In terms of Truth to be found, one idea came to mind about the franchise as a whole. By giving legitimacy to the Bible(Raiders, Last Crusade), an African tribal legend(Temple of Doom), and now the Crystal Skulls, what philosophically must be true according to the worldview of these films? Seems to me it must mean that all ancient religious stories are true, or none of them are. Smells like relativism. Nothing intentional I'm sure, and these movies have never felt preachy. Just a little observation.
The film might also lead to some interesting discussion about the ancient Mayan calendar and its prediction of the world's end just a few years from now.
Rated PG-13 for adventure violence and scary images