There are now two per-usage options for iPad 3G data plans through AT&T:

1. DataPlus plan, $15/month, capped at 200MB/ month. Extra data costs $15 for 200MB blocks. Not sure if this is prorated if you go over by a little bit.
2. DataPro plan, $25/month, 2GB/month cap. Extra data costs $10 for 1GB chunks.

While the DataPro plan is obviously a better deal if you’re going to be a power iPad data user, it’s going to end up costing a lot more. AT&T claims the majority of consumers are not using up their 5GB caps on the iPhone. That’s probably because they never allowed tethering. They will now, for the next iPhone, but it’ll cost you an extra $20 in addition to requiring the DataPro plan. That means $45/mth to let your iPhone be a tether so that your iPad (WiFi-only or 3G models) can share the data plan.

By comparison, Verizon’s Palm Pre Plus phone has a Mobile Hotspot feature that allows tethering of WiFi devices at no extra cost over the data plan (roughly $40/month), which is capped at 5GB. What do you think is the better deal, aside from the fact that the new iPhone is expected to have a much longer battery life than before, and Palm Pre Plus’ tethering drains the battery within 3 hours or less.

If you were plan to use your iPad in all the amazing online ways that Apple’s commercials suggest, it’s going to cost you. Forget watching video on the go, because that’ll eat up your data plan in short order. AT&T claims this is a new lower-priced wireless data plan intended to make mobile Internet more affordable to more people. Unfortunately, power users get punished, but this sort of plan change has been part of the cellular industry for years.