The MEP modeler is pretty sweet and we have been getting deeper into it day by day. It transfers autocad mep information seamlessly and is definitely the step in the right direction for Archicad. Though the collision detection shouldn't just be for MEP vs Architectural objects it should be for all objects including MEP objects itself. More often than not the issues in the field are MPE systems trying to run through other MPE systems, as well as into architectural or structural objects.
Optimizing the BIM is what the MEP add-on has started to do, though if I have a cable tray running into a 14" chilled water pipe and I don't have the room to change the clearance then this is an issue that should be DETECTED before construction with this add-on.