If the last batch of rumours turn out to be true, and O2 is planning to stock the iPhone, then they'll have to do something about their on-line billing system; it can't be accessed by most Apple Mac users at all.
O2 have confirmed that on-line billing isn't supported on Macs, but they reckon it works with Firefox on Panther and might work on other combinations, if you're lucky.
The good news is that from June 2007 all services that O2 develops will be supported on all the popular browsers; including Safari, though the iPhone version of that browser isn't explicitly mentioned.
One might think that any company intending to sell the iPhone would already have a Mac-friendly architecture in place, but that would assume the technical development and top management communicated with each other: something no mobile operator has ever achieved. ®