Right now, very few programs take advantage of the speed. Things are just mildly smoother. But soon you should see lots of videogames that can dynamically load massive amounts of data, letting you switch levels in a second or have highly detailed levels that don't need to worry about fitting into memory all at once. (Presumably the latter will be optional for most titles.)

See the first half of https://www.youtube.com/watch?v=fqi09JnJHOo It's partly a comparison against hard drives, but it gets into why you'd want gigabytes per second.