Doesn't the iPhone, for example, turn off the hot spot capability after awhile if there isn't any usage to save on battery life? So if, after 30 minutes, you want to do a quick lookup on the iPad you have to enable it on your phone again?
Of course, if you are tight on money, but still can stretch for an iPad, you can save $130 on a wi-fi model and save on the data plan for the iPad and pay for hot spot capability.
It would be nice if ATT provided a way to share data between a phone and a iPad. Then you wouldn't have to pay for 3gb on an iPhone and for a separate data plan on the iPad if the 3GB generally sufficed for combined usage.