It's what can you do with a 40 mbps upload speed that you can't do with 1mbps?
Which is, you know - a lot. In the age of user created content, telecommuting and cloud services being unable to upload faster then 128 kilobytes per second is a killer.
If you're dealing with any type of multimedia content you can be needing to move 10-20 megabytes per cycle between a few people with ease - that time adds up, and it constrains how you work.