Wireless datacards & USB with contracts?

[Badger_grr]

Just wondering if anyone has had exeperience with these types of internet acess contracts where you plug the adapter in and pay monthly. I know vodafone and t mobile are doing some but have never heard anyone talking about them

this is what i mean if anyones confused,

http://shop.vodafone.co.uk/index.cfm?go=dataproducts.mobilebroadband&planDuration=24

thanks