I see it something like: http://www.wolframalpha.com/input/?i=Plot[%28Sqrt[Pi]+Erf[3x...]. At first, you can use it and get something done, but it isn't useful. As you learn more, it becomes slightly more useful, but not much, until it hits a point where you finally understand the interface, and can use the features to their complete intent.

Having thought this through a little more, it seems more like bumps. For example, you can't do anything with Vim until you learn basic motion and insertion. That a bump. Then, you learn how to use the more complex motions, and get another bump. With something that has a steep learning curve it is done in bumps, rather than being smooth, because partial knowledge doesn't help any. If you think about it, if you only know the j and r commands in vim, you're not going to be doing anything at all, you're going to need to know at least hjkli before you can even use it.