I've recently ditched BT in favour of Sipgate via my 2mbs Virgin cable
connection and I am very pleased with it.

The call quality is good and I recently downloaded some big files
while making a phone call with no loss of call quality.

I've wired all my home phone sockets up to the Sipgate box and I'm
just enjoying not having to give money to BT any more.

Sipgate has lots of good features although you can't take your BT
number with you.