I believe we have been very luck in the UK. The new O2 iPhone contracts appear to be really good value. I chose the £35-a-month deal over 18 months and I get 600 minutes, 500 texts and unlimited data. On this deal I got the iPhone for £159. In addition to the basics I get unlimited free access to two of Britain's biggest hotspot services–BT Open Zone and The Cloud. I am already making full use of these services. The Cloud is in my local pub and I can find BT in Caffe Nero coffee shops and loads of other places.
There is some method in O2's linking with these WiFi services because while you are using a direct WiFi connection you are not using up O2's data allowances. In fact, I will be surprised if anyone manages to use more than 300 MB of data a month over the cellular network. Of course, if O2 and Apple permitted tethering (using your phone as a modem for a laptop) data usage would jump into the gigabytes.
For the moment I am paying Vodafone £15 a month for 3GB of data use on my MacBook Air, but eventually it would be nice to have everything under one umbrella.
When I return to Greece I will have to visit Vodafone Greece (Apple's partner there) to negotiate a much worse deal than I can get with O2. Instead of unlimited data they give a miserly 200MB a month (is this a Greek joke?) and only 100 minutes/150 texts. On the plus side, the contract iPhone is unlocked and can be used with SIM cards throughout the world. It's at a price, though–€459 or £375. Incidentally, you can buy an unlocked 8GB iPhone WITHOUT CONTRACT from Vodafone Greece for €499 (16GB is €569) and this is a better option than jail-breaking a locked phone in my opinion. For anyone with contracts in more than one country it makes sense to buy unlocked.