Okay I voted very hit and miss, 50/50. In my experience speaking to ntl customer services reps, most of the time they've been friendly and helpful - or at least it's seemed that way at the time. Sadly half the time, either what they tell me is wrong, or they don't do what they say they are going to do.
I've been with ntl for three years this month, and have moved home twice in that time.. each time was a major pain, with setting up new direct debits, being wrongly billed, having to phone multiple times to sort everything out etc.
A few weeks ago I gave a month's notice to cancel my phone and TV services, and instead have ntl broadband installed (I was previously using ntl dial-up @ £10pm). When I phoned I was told to cancel both my ntl direct debits, and that I would be sent a new direct debit mandate form to complete and return.
Some time later, no direct debit form having been received, I phoned again to request one, which turned up a few days later. This is my experience with ntl time and time again: you have to ask several times for something to be done.
Anyway, of course the direct debit form was not filled in - why don't they send a pre-filled-in one, for you to just fill in your bank details, sign and return? So I phoned ntl to ask what my broadband account number was. I was told I couldn't be told this over the phone, so he would post it to me that day, 1st class. Several days later, having not received it, I phoned again, and another chap told me he would send it out. I received it this morning, postdated yesterday, which means that the first one was presumably not sent?
Well, guess what.. my broadband account number is... the same as my telephone account number. Which means
I didn't need to cancel one of the direct debits, which ntl told me I should cancel 
Three unnecessary phone calls, and wasted time.. this has always been my experience with ntl.
Oh, I forgot.. after cancelling the direct debits as I was told to do, I then received a bill for line rental (£18) + £2 non direct debit handling fee!
Happily the billing department were happy to credit me with the £2 (I paid the £18 over the phone with my debit card), and said that the excess line rental would be applied to my broadband account. But why is everything such hard work??