The review process is completely random. One day they accept your app completely, the other day your "iPad screenshot is a strechted iPhone image" or something. Its just frustrating.
In 80% of the cases they never even logged into the app before giving us the OK (all logins and actions are logged, so it is easy to tell)
About 20% of the updates to my app get rejected for no reason other than that the reviewer clearly didn't bother reading the attached review instructions. I have a hard time thinking that _all_ of them are this stupid, so nowadays I started thinking they do this on purpose.
Wouldn't you just assume "about 20%" of them are that stupid?