How much data is enough for your iPad?

Wondering about the 3G plans that AT&T will be offering for the Apple iPad? Is 250 MB spread over a month enough?

If you already have an iPhone, you can find out. I just noticed that AT&T has added a “View Past Data Usage” button to their web site. For me, the cheapest data plan would be fine — I must do enough of my networking while connected to a WiFi network.