As a rule I would stay away from any cashback/redemption offers. First of all I was rubbish at keeping track which bill to send, which form to use, but e2save was rubbish with processing the claims. If I did not use Special Delivery to send the bills the bills would be “lost”. Then the company changed its policy to allow 90 days to claim the cashback (that what the guy over the phone told me), then when I got the T&C it said that I still have 30days to send the bill, they have 30 days to process it and another 30days to send the cheque so 90 days in total.
I now stay away from that sort of deals, either auto cashback offers after 28 days from signing the contract, or just a cheaper line rental.
Regarding 3 as a network, I’ve been with them for the last 3 years and had zero problems. The signal is good in and around Edinburgh and even if you are somewhere rural and can’t get a 3G signal from them then they just use O2 antennas and if you have data roaming switched on the internet is still free.