I have at least two complaints and one comment:
Complaint #1: Everything seemed to fall into place for Episode IV too easily (like when Palpatine just decides, completely arbitrarily, it seemed, to give Anakin the name Darth Vader, or when Padme delivers: she immediately decides what to call both of them, and is nearly dead when she does it).
Complaint #2: Things seemed goofier than usual. Like that stupid lizard thing that Obi-Wan rode, or those wooden (?) helicopter-like machines. And the fact that Palpatine laughs evilly at every freakin' oppurtunity he gets, especially when he's fighting Yoda. My friend compared him to a video-game boss - the type who systematically throws something at you, then laughs (at which point he is vulnerable to attack), and then throws something again, and so on.
Comment: I thought it was kind of odd how, between every episode, and even sometimes within one episode, war machine design (fighters, capital ships, tanks, etc.) drastically changes, yet the droids hardly ever change. The type of droid that R2-D2 is has been in use for all six episodes! It would be like the creation of a super-advanced fighter jet that uses a 1960's navigational system.