You can do pretty much any UI you can imagine using a website in some way and Atom allows you to do exactly that. You can modify the entire UI and this is what I was always missing in ST: The ability to modify the UI more extensivly.
Sadly, this all leads to the very downside that everyone knows: Performance.
Computers will eventually get to the point where Atom feels as fast as Sublime, because
1) the coding was improved and more significantly, and
2) CPUs will get good enough for Atom that a human can't see differences between Atom and ST's performance, despite ST being way faster still. It's always been like that.