I've done a Plone 2.1 to Plone 5 and Plone 4.3 (Archetypes) to Plone 4.3 (Dexterity) migration using this toolset:
collective.jsonify
collective.jsonmigrator
collective.transmogrifier
mr.migrator
plone.app.transmogrifier
transmogrify.dexterity
It took me countless hours to get everything right. But now it works fine and new migrations are done much qicker. I planned to write an article but some project related time constraints prevented me to do so.
Regarding the GUI: mr.migrator lets you start the migration and do some config settings from Plone itself (via the @@mr.migrator view).