I needed to import 9000+ users from an external MSSQL DB and once we created the basic csv export, the initial tests on J2.5 worked flawlessly the first time. J3 failed as the Joomla "usertype" has changed from 2.5 to 3.x. I contacted the developer and within 24 hours they had updated the extension for J3 to allow the user import to work in J3. I am pleased to no end with the extension as well as the support I have received from the Joomlarra team and I definitely recommend this script if you need to migrate/import users. I previously used 'userport' which is fine for J2.5, but this script works with 3.x AND has a much larger feature set to work with. Excellent!