I follow the instructions and the migration occured but for some reason a couple of items failed (I think my site is a bit old an intricate). Since I couldn't use the migrated 3.1 site I was going to ask for a refund.
Cyend were professional in their approach. They offered me the possibility of a refund but also offered to help me sort out the issue with the migration.
In the end they sorted out the problem and now I have a working 3.1 site on which I will have to make some adjustment but the migration saved me lots of works.
Totally recommend them. They were responsive in a timely fashion, concise and effective in their approach.