Depends where and when you connect, I guess? You probably know more about it than me, It's just what I was told by the installation guy, that you get far closer to the speed than with a phone line (I have a TalkTalk broadband 8mb service, too that I get about 3.5 from (must be quite far from the exchange)
I've always found cable pretty much spot on. Although I'd like to see what BeBroadband could offer me - I guess the 24mb would be less than half that considering my TalkTalk is less than half of the 8mb.