What have you tried though? I'm on vanilla Talktalk LLU. I notice for instance my uploads slow from ~90kB/s down to 10kB/s or much less between 6pm and 9pm or later. I also get dropped repeatedly from chatrooms that I've been constantly in for the last 9 years during those times of day. This is with the winmx protocol.
Do you torrent? I know overnight is ok but I'm thinking more of the daytime/evening speeds.
If Opal use the same kit in the exchanges and if the kit decides the shaping etc then I don't see how the service is different. There were some 'ifs' there though