I had been with vodafone for quite sometime, mainly due to the price.
but since i got my "your bill will be increasing" email, i noticed the service fell through the floor.
it killed my on-line gaming with pings going from 30ms to 5 seconds, which made it pointless.
moved to Sky, and not had a problem since, and downloading files (and speed tests) are much better.
Couldn't recommend Vodafone less to anyone