I was previously with Zen but decided to try BE as they provide LLU at my exchange. Only been with them for about 4-6 months, and though it's not been completely problem free, I've been pretty impressed. I've been able to keep in touch with support staff via the forum, and email (haven't had to phone yet so can't comment on that), and while I wouldn't rate them as highly as Zen support, they seem pretty helpful. Even better, I haven't needed them at all for the past few months, and I'm paying not too much more than I was with Zen, but have faster downloads, lower pings and what now seems to be a reliable connection. I'd recommend them.
Incidentally, after suffering BT Broadband to start with, I'm pretty careful about who I use for my broadband, I'd never have considered BE if there was any real suggestion of people not rating them?
Edited to add: I'm pretty sure that the BE support is entirely different to 02, and is one of the reasons why 02 isn't rated as highly as BE.