I think the main problem with the specific example is that a list is the wrong data structure to represent a polynomial. Even a simple `IntMap` would be better, where the key is the power.
I'm primarily a haskell developer and most haskell source files are relatively small so I don't have too many issues with speed or lag. I just love atom, the look and feel, package installations, extensibility ...
Over the years I've gone back and forth between Sublime, vim and emacs. Atom is the first editor I really love. I've been using is for about a month now for serious haskell development. Yes it's still a bit slow to start up and a little buggy but it's not even at version 1.0 yet. I just really like the UI and the simplicity of installing and configuring packages.