I had some headaches yesterday while trying to upgrade to VMWare Fusion with Vagrant.
The steps that work are:
- export your boxes from Virtualbox to OVA files
- run 'vagrant destroy' on all your boxes
- uninstall Virtualbox using the uninstaller script in the installer DMG
- download VMWare Fusion
- run 'vagrant plugin install vagrant-vmware-fusion' to install the provider plugin
- run 'vagrant plugin license vagrant-vmware-fusion license.lic' to install the license you just bought