This project looks great. VirtualBox runs on Solaris, an OS which supports writable snapshots and deduplication in the ZFS filesystem. Is there support for filesystem snapshots in Vagrant? It would be nice to spawn a new virtual machine from an existing on-disk snapshot.
I know Vagrant runs on Solaris, but I haven't done anything OS-specific for it, so I'm going to say "no" to this. Hit me up in IRC and we can talk about it.