Written on: 26/07/2012
Having been on all the networks over the years O2 is by far the best. Always have a strong signal and fast HSPA+ internet. I also find that O2 signal (and voda i think work on the same frequency) is good inside buildings/shopping centres etc (better than the other networks) as O2 work on a lower frequency to penetrate buildings.
I have been with O2 several years now and have just upgraded from iPhone to Samsung S3. The whole process was seamless and so helpful in store and the call centre customer services. The store took the time to show me the differences in android, got me started on the phone and didn't rush me at all. Then I called customer services to have my iPhone unlocked as I wanted to keep it to put my work sim card in and they unlocked it at no charge and hassle free.
Some people seem to think O2 are expensive? I don't see that really I think its good value and at the end of the day you get what you pay for like with anything (Tesco Value vs Tesco Finest is one way to put it I suppose!) Id rather pay a little more for a quality network (but i dont think they are expensive anyway).
Summary: great signal, friendly UK based customer service, reliable.
The thing with mobile networks is different people have different experiences. I get why there are negative reviews, there are for all the networks because some peoples experiences are worse than others and to be fair I would have written bad reviews about my experience with other networks (particular Three who are dire). If you are reading this with a view to change networks I would recommend O2 but they may not be the best for you. Either ask friends and family about their network signal around you, or get a PAYG sim to try it out before you get into a contract.