i had a horrible experience with the NCT when Calvin was 4 months old. (this was in dunstable, bedfordshire).
i went to my first mom/baby group. and sat there. ignored for 45 minutes. and when i got the courage to talk to someone, she got up mid-conversation and left.
perhaps it was just bad coordinating on behalf of the group planners, but it was enough to put me off the NCT.
not to mention, when i consulted the NCT for breastfeeding advice, they were VERY militant about it. and when i mentioned giving some formula too, i was told, "oh no, you don't want to do that." and so on and so forth.
its worked for some people i know though....