for a little over 2 years.
No significant problems.
Tech support is via email, not over the phone, but response, when needed, has been quick and, generally, good.
I had some duff info regarding a use of a router shortly after I joined, and a webspace problem that they couldn't reproduce, (and mysteriously disappeared). My only other dealings have been recently, regarding speed. They dealt with that well, getting BT involved, and all is now well.
I certainly wouldn't put any off using them, but as I have no experience of any other BBand isps, I can't say they are better than any others.