The iPad models that come with Wi-Fi and 3G will let users choose, on a month-by-month basis, whether to pay AT&T for 3G data service at one of two service levels. The unlimited plan is $29.99 per month, just like the iPhone's data fee; the 250 MB per month plan (combined upload and download) is just $14.99 per month. Will that suffice?
I too didn't think 250 MB a month would be enough until I looked at my own iPhone usage data … since I got my 3G I have averaged less than 100 MBs a month in usage. I am sure there are months when I use more than 100, but 250? The crazy thing is that I keep wifi off most of the time because of the VPN issues I have at Penn State. I think I can manage on 250MB a month. That is a huge surprise to me.