Our checklist:

Create a vanilla 2.1.4 site, install CMFMember, attempt migration on default CMFMember

Move ZODB from 2.1.4 site to 2.5.1 that has CMFMember, Membrane, Remember

On 2.1.4 add an extended/custom CMFMember type/product add some members

Develop a custom Remember member type

Move ZODB from 2.1.4 to 2.5.1 site that has CMFMember, Membrane, Remember

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Actual setup: python 2.4.4, zope 2.9.5 across

Site1: plone2.1.4, CMFMember from Plone.org prepared package.

Site2: plone2.5.1, five deleted for zope's five, member and remember from svn trunk.