Saw this on Thursday, and I pretty much agreed with every review I've read (you know, the ones I trust; not The Mirror or something which no doubt said it was the best film ever made). During the first hour Spielberg evokes 1950s America brilliantly - the fact is he's so huge that you forget that he's actually a decent director... but it's fun and colourful without being too Happy Days. Oh, and there's one set piece involving a village of mannequins and an atomic bomb which is one of the most awesome things I've seen on screen in a long time.
But then the story moves to classic Indiana Jones territory - a temple in Deepest Darkest Peru, and things started to go downhill pretty quickly. There's an awesome twenty-minute fight scene in the Peruvian jungle which kicks ass, but other than that it's pure silliness, and while I normally consider that a good thing, it just gets ridiculous.
As for the performances, Harrison Ford can still do withering sarcasm brilliantly and still convinces during the fight scenes; and Shia Le Beouf as Mutt Williams is a fantastically charismatic addition to the franchise. The chemistry between himself and Indy is probably the highlight of the whole film. Oh, and Cate Blanchett clearly has loads of fun as the Russian femme fatale Irina Spalko.
It's not great - it's far too unbalanced for that - but I'm happy to have seen it on a big screen, it's better than Temple of Doom (imho and all that), and basically I'm just glad to have Indy back.