Hi,
Which carrier is better how to set up and use?
I am living in UK and I am with O2 iPad data plan.
O2 is very easy. I just put Micro SIM card and one plug in to my Mac and iTune downloaded something and then in Settings/Cellular Data/ set up automatically and login register screen come up to create account.
Then in Cellular Data/ view account, there is O2 software screen open each time when you want change plan or top up.
Type E-mail and password and you can view your plan from there, even you have not got enough top up left.
I can pay by card each time when I want to use.
I do when I need to use just pay £2/day in UK.
But £10/month and £15.month plan is recurring plan. They charge every month.
I just wanted Pay as you go type for iPad.
I have a iPhone too. I do not need go to internet all the time by my iPod only when I want write a long e-mail or want see web site I use iPad.
This point, I think O2 is very good.
O2 is geared up for Apple standard, even iPhone, O2 has "Visual Voice Mail" which very very useful when someone left message you do not need dial 121 or get text or something.

When I went to Italy, I bought Vodafone Micro SIM for my iPad.
I thought all same as O3 set up for iPad, but was not!!!
You do not any screen to create account, not from iPad. You can not top up from iPad. You can not register from iPad....
Settings in Settings/Cellular Data/ I have to type Vodafone APN manually input APN in setting which written in the web site. Otherwise not able to surf in internet.
Later, I discovered there is APP application for Vodafone Italy in UK iTune store. This app you can see how much you spend etc...but I think you still have to go to the shop to top up for my iPad.

Be honest O2 in UK for iPad is the best, I did not do anything for the setup and so easy just like Apple planed.
If anyone know other carriers how different, please tell me.
Not only how much cost for the month and data etc...
How easy and how to pay and cancel, top up, or software etc...
Thanks.

Pay and go? With O2 in UK only if you have a credit card with uk billing address. If you are a traveller and you don't you are not allowed to pay neither using credit cards from another country nor cash. In Italy I was able to pay cash and go using Vodafone Sim....This information about the uk was provided by the O2 and Orange stores located in the strand nearby charing cross tube station.