I have the vodafone BB + anytime package, never had a problem (I'm in Dublin area). Although I have seen here people complain about them. I did a tech.problem once, not Vodafone's problem really, it related to Eircom line replacement or something. I have to say my one complaint was trying to get thro to Vodafone. Once I got thro they were fine, but I was waiting ages. Then again, that seems to be the norm!
A friend has the UPC deal for internet +TV,no phone, both are fine. I did have UPC for TV only a few yrs back and found them awful to deal with - even Joe Duffy got involved with a string of complaints! (not mine tho). That said, I hear they have worked on improving the service, but personally I would be reluctant to go back. Maybe you should check with a few neighbours and see what they have before opting one way or other? Sometimes it seems as service is very much a localised, as to whether it's good or not.
PS: when you say NTL, I assume you mean UPC?