I think it is the combination of consistency and adaptability. There are a huge number of interesting features and tweaks out there, and every once in a while

I think it is the combination of consistency and adaptability. There are a huge number of interesting features and tweaks out there, and every once in a while one encounters a useful gem. For example, I have started to use Unicode more heavily in documentation, and I am also a latex user, so now there is a mode which lets one enter any kind of unicode symbol by typing the latex sybol name. Or another, I found that syntax highlighting is neat but what is really helpful instead is to give any identifiers in functions different colors, which makes the data flow in the function much more salient and quicker to understand - including spelling mistakes. And that works in many languages.