After years of using Eclipse, my eyes have been trained to seek an error indicator in the left gutter. Intellij's default error indicators are on the right, as little decorators in the scroll region.
So, taking matters into my own hands, I've created a plugin to display a gutter icon on the left if there is an error on that line.
To build this plugin, clone, import project into Intellij. Select Build->Build Project.
Once successfully built, you can select Build->Prepare Plugin Module 'erroritem' for Deployment.
To install jar, visit Preferences->Plugins then click Install plugin from disk...
...Or, with any luck, this plugin is available in the JetBrains plugin repo...
Enjoy!
CG