I too left o2 earlier this year after being with then for the last 8 years. In previous years it has come to the renewal date, phoned up and been given a discounted deal to stay and for being a loyal customer etc, but not this year. Got told the best they could do on a htc desire was a £40 month contract as I needed a smart phone contract for 24 months. Used to pay 15 a month with a 7.50 a month web bolt on so not sure what extra the smart phone contract would have given me. Anyway, went with orange in the end, free phone, £25 a month and an 18 month contract. Happy days.
Sad thing is tho, I was more than happy with o2 all those years and would still be with them if they'd have been more competitive or even a little bit closer.