As someone who switched
I had been a Blueyonder/Telewest/VM customer for 4 years before I switched to Sky last month. I've always been a great fan of the broadband offering, and because of that I've put up with the shortcomings of the TV they offer (no interactive services to speak of).
I'm a HDTV subscriber and with VM offering almost no HD content, my extra £10 a month was promised to be refunded each month. This happened once. So I started looking into switching to Sky.
I was amazed to find that for a better service on almost all fronts (Broadband is on a par at best, but I get more and better TV, better phone service and a PVR that works), I'd actually save £25 per month!
The switch went through fine and I've got nothing but praise for Sky's service.