I agree, at these speeds, there are going to be other factors in play:
1- Price 2- Reliability 3- Tech Support / Customer Service 4- Ping Times 5- Ability to Run Servers
There is no real need at this time for 15mbs connections. Until other services are offered over the internet (VOD, TV) 99% of the users would rather pay $20 for a 3mbs connection than $50 for 100mbs connection.