Before run generated application with command mvn gwt:run do not forget that webapp content has to be copied.
To achieve that you can change your pom.xml by adding <copyWebapp>true</copyWebapp>.
It should looks like below:
So once I click Launch Default Browser everything works fine and app is properly compiled.
You can import your generated app to Eclipse using this plugin: http://gwt-plugins.github.io/documentation/gwt-eclipse-plugin/Download.html .
I've successfully imported it to IntelliJ IDEA.
Also the super feature GWT Super Dev Mode works just out of the box. After I changed something in the Java code I could simply refresh browser to see the changes!
That's because -Dgwt.superDevMode parameter by default is set to true.