Speak as you find - my experience of o2 Customer Service (when I needed it) was outstanding. The fellas there could not have been more helpful.
I have an o2 mobile phone and with them for my broadband, but am tied in to BT with a contract for about another seven months. Looking to find out how to cancel the "continuing contract" with BT. When I do I shall certainly consider o2 for my landline.
I'm somewhat surprised at morddwyd's comment, as I find o2 perfectly acceptable.
Yes, their front line staff are not super technicians, but then they're not meant to be. And as Barmoor commented, they certainly try and be helpful *and* at least you're not paying premium rates to speak to them. In fact, you're paying nothing at all!
When I called o2 about a fairly complex server configuration issue, they couldn't answer me (I didn't expect them to), but did offer to raise the issue to a level two technician, who could potentially have raised it still further. In the end, I managed to sort it out myself, but the offer of help was there for all that.
All I can compare in recent times, was a conversation with the Virgin help desk on behalf of a friend, and by comparison, they were a disaster, offering totally false information.
Never had an issue with their technical expertise, or their mobile service (one of the reasons I changed)just their broadband helpfulness, or lack of it, and I moved from Orange, not the highest in customer satisfaction ratings, and about which many people would say anything would be an improvement!