I've just opted for the 2MB basic service, but still have NTL/Virgin. My thread is here:
http://www.cableforum.co.uk/board/63...witch-not.html
So far, it all looks good. High ping times but as the link that Matt D provides explains, this is normal. Internet browsing is fine - better than NTL. Downloading seems fine also, though with NTL I get about 3.5Mbps whereas with Sky I get 1.7Mbps
[edit]Oh and a filtered face plate is a must, as is ensuring your internal telephone wiring is good quality. The extension I'm currently using is 6 core cabling with IDC connections, properly done. No dodgy screw connections. I intend getting a face plate - doddle to install.