The horror stories usually are about their Caribbean routes. I think the flights to LGW are noticeably more reliable. The service is also noticeably better with free meals for one thing. And you can't beat the price -- on one flight I couldn't pass it up and I flew Club class for less than it would have costed in economy on AC (or even US) last year.
However in the end they're not a mainline airline. If the plane you're scheduled on has a problem they don't have another flight in a few hours and they can't just wheel out another plane. You're going to be waiting until they get the plane fixed.
What cruises start in London?!