I havent tried Skype yet via NTL, although I dont really plan to as I only use a laptop at home and found that being tied to the computer was a bind. The appeal of my Voip solution is that I use my "proper" DECT phones and you cant really tell its not a land line. I even have an 0191 local number. The perception is that nothing has changed.
I think its important to stress that it is pushing the upload bandwidth of my 1MB link to the limit, so it is possible I may experience a little breakup in the future if I am heavy utilising the link, but I guess Qos will handle that (dropping or delaying other packets if required).
You could get yourself the Netgear adapter (also a router should you wish to use it as one) from
www.sipgate.co.uk. You get 555 minutes free as soon as you hook up and register tha device, and its totally free to have a SIPGTE account. Otherwise you could just try their free softphone on your PC (but I found this unlcear and a bit like jittery like other soft alternatives)