I'm with Virgin, I get 7.6MB bandwidth on an 8MB account, over a BT phone line (BT could only manage 5.3MB) - that I'm impressed with!
If the landlord was to allow cable I'd have it, as soon as I move I'll get it.
Virgin were the first ISP to offer 10MB, 20MB,50MB and very soon to be 100MB connections.
All ISP's will struggle with bandwidth at peak times, no matter how good, or bad, they are, there's a limit to the amount of data any phone line or fibre optic cable can carry.
Imagine sending 100 trucks into a tunnel, one at a time - no problem, simple and quick, 100 at a time - big problems! Get the idea?
As for customer care, I don't have case to phone them very often, but the times that I have, they've been quick to answer, polite and helpful.
I'd recommend Virgin to anybody.