Serialization via Data::Dumper or Storable seems to be the Achilles Heel of all of the inside-out implementations. It seems to me to be a Very Bad Thing(TM) that, by default, including a reference to almost any inside-out object in a larger data structure results in a data structure that cannot be serialized. And, of course, fixing that would require making it possible to break encapsulation via manipulation of the serialized instance - thus defeating the raison d'ętre of inside-out objects.
I also severely dislike the use of 'lexical globals' inherent in them. It makes anything using them difficult to make completely thread-safe.
In the quest for encapsulation enforcement, they may be throwing the baby out with the bathwater.