Speaking as someone who HAS moved away from NTL and gone to Bulldog, there are both good and bad points.
Good:
NO restrictions whatsoever, I'm on alltime 1000 and I'm saving £25 a month compared to my old 3mb NTL
Reliability of service - once up and running I've had no problems at all
Bad
Took 6 weeks to get installed, so 2 weeks with NO broadband at all!
I'm too far from the exchange to get anything other than 1mb
Having to pay £75 to have a phone line fitted, when I have a perfectly good NTL line was a bit gutting
In all honesty, if NTL rethought their caps, i'd be back like a shot, I got used to the lies and misleading adverts etc. with them. But I put my money where my mouth is, I said if they actually enforced the caps I'd leave - they did and I did
It's cheaper and I don't have to worry about the time online, as I have no means of monitoring it, 512k is not a realistic option for me so staying with NTL's crippled product for "heavy users" was not an option.