It's not connected to any plan. If you want 3G service for the iPad, it's $15 for 250 Meg a month, or $30 for unlimited. No plan, just pay for the months you use it, and you can buy it on the devise itself when you need it.
If I get in the habit of taking my iPad everywhere I go, I will get rid of my iPhone, and go with a Nexus one on a local provider. There is one in town that will give me 1,200 minutes, 1,200 text's, and 50 meg of data for $30. All on the Verizon network.
50 meg should be fine if I have my iPad. If I root the phone and turn on tethering, then I will just use wifi on on the iPad, and get unlimited data on the Nexus.
Lots of options at the moment :)







