iReport 5.6.0 Failing Silently

Versions up to 5.6.0 (currently the last one) do not run with JDK 1.8. They will silently fail, at least on Windows 7.
If you want to keep JAVA_HOME set to a JDK 1.8 installation, you can run it launching a batch file with something like this inside:

@echo off
set JAVA_HOME=C:\opt\java\jre1.7.0_71
"C:\Program Files (x86)\Jaspersoft\iReport-5.6.0\bin\ireport.exe"

Customize as needed.