Is it my imagination or are iTunes downloads huge compared to Amazon or even Netflix's new download service? What's the league table of data compression?
One good thing about iTunes is that I'm pretty sure you can download stuff in the background whereas the Amazon iOS app just stops. (Fail.) If so, then this is either just stupidity on Amazon's part, or else due to dirty tricks by Apple and their often excellent, sometimes Nazi policy on app submissions.
It's also incredibly annoying that you can't see the actual time remaining shown in the downloads list in the Amazon app, and you can't make purchases in it, which is utter madness.