After disabling some obvious patches and incompatibilities (Executive, CGX4), my A4000 actually boots all the way to Workbench from a OS3.9 partition but with AROS daily build 'ROM' kicked.
Come on, thats not bad at all!
Graphics are slow but boot time etc is fine. I need to pickup a extra CF card and build a AROS install on it for shit 'n giggles.