I managed to setup an account over the phone, and select a monthly tariff.
But as a previous poster found out, when you go to the web site to create your online account, it wants to send an SMS to your iPad SIM.
But hey, the iPad is not a phone, and doesn't have SMS !
Just spent 20 minutes on the phone to technical support, trying to explain the problem, he eventually clicked! Then said, 'Oh you can't setup an account then, as that is the only way we do it!'
I said cancel the contract then, and you'll have 1000's of frustrated new iPad owners very soon, and he then offered to escalate it and get a senior techie to call me back.
Still waiting ..........