The best thing about this installment was the character interaction. There was much more humor this time, and the familiarity of the main characters caused that portion of the plot line to flow nicely.
The action portion of plot line was a different story. To begin with, Indie's Communist adversary was not nearly as 'scary' as the threat of the Germans. With the Germans we really bought the threat of world domination. Not so much with the Irina Spalko. She didn't really sell the Red Threat.
Additionally, the actions scenes seemed rather forced and flat. Even the score was rather boring--though I don't blame Mr. Williams. He really didn't have much to work with.
George Lucas obviously had to stretch to get this script finished. Many loose ends were tied up, though, which makes it worthwhile. It also makes it clear that George needs to stop now.
I enjoyed the movie because it was Indiana Jones. I would recommend it to others because it is Indiana Jones. On the scale of Indie movies however, I rank it 4 out of 4.