What reasonable use has a consumer sub for more than 10-20 Mbs? if your running a business from home get a business line and stop expecting Pensioners to subsidize your business
2 different people watching high definition video at a high bit rate.
Going from dial-up to 2Mbps ADSL was a huge jump, and ADSL2 also made a big difference. However, for a single user, there's not really that much difference between 20Mbps, 40Mpbs and 80Mbps. You have a faster connection to the exchange, but you're still limited by the speed of the net and the speed of the servers you connect to.