I've used a few different providers now (since I've moved a few times) and I have to say that BT provides - by far - the worst service I have ever seen.
Connections are dropped permanently, latency is high and throughput is unsurprisingly low.
Online gaming is obviously out of the question, but even watching youtube videos becomes a chore when the connection is dropped half-way thorugh and it becomes impossible to watch a video all the way. It should be noted that these are permanent issues. They're not occasional glitches.