If its a good deal your after then go for it, if its for better broadband, just bare in mind its likely that Vodafone use BT's exchange so it will be on the same sort of speed your receiving now. BT are c*nts and run the show in terms of infastructure throughout Britain. Its like monopoly and they lease of parts off of their network.
Can't argue with any of that, I just renewed with BT on Monday, got a letter today to inform me of price increases. Seriously tempted to bin them off straight away but I've also moved my mobile to them from Orange, don't know if I can be arsed boxing up and returning the mobile (at my own expence) and moving my number elsewhere, trouble is they rely on the fact I'll do fuck all and just bite the bullet, twats.
I'm sick of trying to fathom out the best deals, it's all so fucking confusing and they know it.