Call me old-fashioned if you will, but I still prefer Eclipse to any other IDE. That said, I stick to "vanilla" Eclipse plus a handful of hand selected plugins. I try to avoid vendor-built versions like STS, anything branded "WebSphere", etc.
Note that if you use the latest version of Grails, you no longer really need a dedicated Grails plugin for Eclipse. Use the Groovy plugin, Gradle plugin, and the standard HTML editor and you get pretty much everything except for perfect highlighting, and code completion, in GSP files.
I just can't get IDEA to respond to clicks in less than 10s. There's obviously something wrong with my setup.
That may be idiosyncratic but if you happen to match, there you go. Either turn off relative line numbers (absolute are fine) or ligatures.
However, after being frustrated for long enough, it motivated me to make my own that is more of modern command palette for Eclipse.