I know three people who are on them and two of them have had serious problems.
The cancellation problem is a major one as your current provider will cancel it with BT which in theory takes a week but often happens within days. Then after the week, TT put in a connection request and that takes another week. So it can result in no BB for 2 weeks if you're switching.
Another problem I hear about is that the cheap BB & phone package deals have gone significantly up in price since they were introduced.
And of course there's the problem of actually getting enough capacity into the system where they switch you from BT to their own equipment which can again take a long time.
Then again, not heard brilliant things about Orange recently either, but better than Talk Talk.
Trev