What does "this" refer to in the following quote from the Wikipedia article on Learning Curve?
The learning curve can also represent at a glance the initial difficulty of learning something and, to an extent, how much there is to learn after initial familiarity. For example, the Windows program Notepad is extremely simple to learn, but offers little after this. On the other extreme is the UNIX terminal editor vi, which is difficult to learn, but offers a wide array of features to master after the user has figured out how to work it. It is possible for something to be easy to learn, but difficult to master or hard to learn with little beyond this.
Edited to highlight the original sentence as given, to distinguish it from the context that was supplied later. —Robusto