I've got Tiscali Broadband. Never ever runs at its full speed of 2.3Mbps even though I can see the telephone exchange out of my bedroom window (it's about 100m away at most). Traffic shaping. Unlimited usage... but you get punished if you hit a set undisclosed limit certain times - they call it a "Fair Usage Policy" - basically means don't turn your computer on at peak times
I think ADSL is just crappy technology, can't wait until I move back into a cabled area again
Seriously, there's not a decent ADSL provider anywhere in the UK - you have to have cable if you want anything like decent broadband.