For me, it's mostly Java and Kotlin. I look for the same kind of things. Things that I like to see:
- Short methods.
- Small classes
- Sensible packages
- Variables declared to Interfaces not implementations
- Single Responsibility Principle applied.
- DRY applied.
- Good names for variables and methods
- Few instance variables
- Few static members
- No comments, because you don't need them
- Uses lambdas, Streams and Optional
- No empty Catch{} blocks
- No f*&^*cking! arrays.
I can generally tell in a few minutes if something is going to be a pain to work with.
It just works. I spent years with Eclipse (but quite some time ago now), and it was always a pain getting particular things to work properly. The last time I messed with it was doing research for an article I was writing. I was try to get Gradle support enabled. I wasn't able to do it, but I admit I gave up pretty quickly because I don't have the patience for messing with tools that don't work any more.
In truth, I really liked the Open aspect of Eclipse and I wish it work better than Intellij. Maybe it does now - I don't know. For Java Intellij is awesome, and does everything you could ever dream for. For Kotlin - well Kotlin is an Intellij product and the support for it is awesome.