I take BT's new offering called Infinity - Fibre to a local cabinet and copper to the property...
The previous rates were approximately 2Mb download and 0.4Mb upload - The advertised rate was up to 8Mb.
With the new service I typically get 20Mb download and from 6 to 8Mb upload - Advertised as up to 40Mb in and up to 10Mb out.
I make semi regular tests by going to Speedtest.net
My wife who sends business mail with attachments notices the benefit of a much faster upload speed - her "sent" messages go much quicker.
I notice virtually no difference in the way the screen of my browser is refreshed or painted - even though the data rate for incoming packets is faster - 20 versus 2 -any improvement on my screen is difficult to notice - packets from the internet arrive at the speed of the slowest segment of the overall network - sure they come whizzing in to me at 20Mb but then the system has to wait for the next packet to arrive.
Google Chrome is much faster than my other browsers.
Some computers in the house give consistently higher test speeds than other computers - I put this down to the wireless cards but that's just a guess.
Make regular tests using speedtest.net and note down the results - then you will have something to talk to the ISP about.
My test just now to a server less than 50 miles away reported 20.33 in and 7.77 out
Peccavi
January 2011