I have been with NTL for a few years, between 1999 and 2004, on their NTLWorld package. Technically the service is reasonable, but their customer service is distinctly mediocre. You can't expect much, if any, feedback on the rare connectivity outages, instead relying on frequent attempts to reconnect.
Despite its shortcomings, NTLWorld wasn't bad value in the old days, but nowadays (late 2004) it looks decidedly overpriced compared to the ADSL marketplace. Raising the bandwidth amounts has helped to narrow the gap, but it still seems overpriced.