Yep, round these parts it's not worth paying for one of these 8meg services as we cannot get close to that. Also as I understand it, contention is pretty much the same at 50:1 for all providers if you are on a home service, and unless something special is done, this limit exists at the BT exchange, so nothing I can do about that.
I would suspect the places where BT interconnects with my provider's pipe (AOL) is pretty solid, AOL may have dreadful client software but I bet their network is pretty good. I also suspect a lot of these specialist providers who charge a little extra are simply reselling a large provider's service anyway.
So what's the real difference between providers? Customer service? Never needed it, service only goes down when there is a thunderstorm (and occasionally the storm takes router power out too), and they cannot do much about that.