I changed from BT to talktalk and although it took a long time to get set up, I have had no problems with it at all. I had constant problems with BT so am so relieved to have a good service now. And you get free international calls to selected countries, fantastic if you've got relatives in Canada and the US.
In all honesty, I work for sky and would be worried about the broadband service...it's not widely available and I'm none too sure about the customer service for that dept... until they have a few months under their belt I'd steer clear just in case something went wrong...but the deals are quite good anyway
I am with Tiscali and have been for over 4 yrs now, coming upto my 3rd yr on Broadband, I haven't had any major probs, Mine is £12.99 per month and that is unlimited, and it is roughly 2mb which is plenty fast enough for general surfing, Tesco also do Broadband, depends how much you want to pay