Two things I would love that would make my Codecademy experience better are:
1. Change the 2nd and 3rd panes to a horizontal split
I like the lesson information on the left taking up the whole height of the page but when it comes to actually writing the code, unless I'm fullscreen on a 27" monitor I can barely write code without constant wrapping interfering with my indentation.
2. Give me Vim keybindings
This is much more specific than the first wish but man, once you're used to Vim you abhor normal text navigation. Its interesting that some online tools have it (JS Bin) and other, more prominent ones don't (Atom). I would like it if Codecademy did have this option.