This one is for the iPhone people on my flist (I know there are a few of you). How much data transfer would you say you use on average each month? I am looking at different plans I can get when I eventually get an iPhone.

I'm looking at different plans that come with 500MB, 1000MB and unlimited (last one is expensive!), trying to see what I can afford while still a poor student, so any insight into what you iPhone users have a month would be helpful!