I really enjoyed it, and thought that it fit in well with the previous 3 films. While it wasn't as good as Raiders or The Last Crusade, i did enjoy it more than Temple of Doom, so overall i was happy with how it turned out.
The only things i didn't like was the fairly sedate opening (what was the point of those totally random kiRAB having a car chase with the soldiers???), and Shia Labeouf's monkey impersonation.
I loved how the Janitor from Scrubs was playing an FBI agent! I couldn't take him seriously at all, lol.
I think this film should be treated like The Simpsons Movie last year in the way that you should ignore all other opinions on the film and just go and make up your own mind. Most opinions/reviews of Indy 4 will have been presented by people with rose tinted glasses (or fanboys, like the people who absolutely hate the Star Wars prequels, even though they honestly aren't THAT bad...well, maybe Ep 1 is, but the other two are decent films). These people are expecting the second coming, and just because it's not what their vision of the film could have been they give it a critical drubbing. Anyone who has yet to see the film and has read this thread will probably assume that it is mediocre to bad, and imo it far from either of those things.
PS: I'm not having a go at anyone in this thread, you all have a right to your opinions.