We were on Orange, but deserted about a year ago. The central Royston area had lost a tower (a car rammed it), the local nimby tendency wouldn't let a new tower be erected, so between the lack of new capacity and loss of existing capacity, we were usually unable to get signal at home.
So we made sure demand declined.
Apart from that, I generally liked Orange, and if we hadn't lost what had been good coverage, we'd have stayed.
She went for 3 (best option for low usage PAYG), I went for Vodafone. I think we're both happy (well, I was once that half hour phone call to my Mum from Hiroshima got down-costed to 75p).
For the iPhone itself - at last it can actually work in Japan, now the 3G has turned up. But whereas the iPod Touch is a gorgeous piece of kit, I did tend to thing the last iPhone wasn't worth paying all the extra for.