For those able to ascertain the downstream attenuation figures from their router or modem, the folllowing graph gives a good estimate as to the speeds you should be achieving..
For example, I'm on an ADSL 2+ service and have an attenuation of 45db, about right for my 2.5km line length. I synch at around 7.2 meg and get around 6.5 meg down (difference down to overheads).
