> One of the big issues that makes library authors reluctant to use metaclasses
> (even when they would be appropriate) is the risk of metaclass conflicts.
Really? I've written and reviewed a lot of metaclasses and this has never worried me. The problem is limited to multiple inheritance, right? I worry a lot about MI being imposed on classes that weren't written with MI in mind, but I've never particularly worried about the special case of metaclasses.