In the UK the main speed factor is the line between you and either your cabinet, or your exchange. You're sold packages that are probably either 8 or 24 MB/s, and you get what you can. I'm 1.1 miles from the exchange directly with no fibre in the road, so I get 6.5 while paying for 24. When fibre comes any nearer, it will be free. How is it in US? Is fibre to the street/cabinet common?