What is needed to make it also work for ManyToMany associations?

May be a better fallback would be do an ArrayCollection->matching() instead of just giving a runtime exception?

Is this something that is difficult to implement?

The schema validator should analyze mapped lifecycle callbacks and:

a) if some lifecycle callbacks were defined, but no @HasLifecycleCallbacks annotation/mapping was set, warn the user
b) if some lifecycle callbacks were defined, but methods are not public, warn the user

Similar to this issue I think, but triggered when performing a query on entities modelled with Class Table Inheritance, e.g.

$qb = $repository->createQueryBuilder('entity');
$metadata = $em->getClassMetadata($class);
$qb->where('entity INSTANCE OF :type')->setParameter('type', $metadata);
$qb->getQuery()->execute();

Seems that there isn't a corresponding entry in the parameter mapping array for this clause, which triggers the exception at line 254 of Doctrine\ORM\Query:

if (count($paramMappings) != count($this->parameters))

UoW currently passes computed changesets to lifecycle event args byref. This has to be changed to force users to use UoW public API to modify changesets instead.