I don't have any experience with this particular product, but done work with a bunch of semantic web software (which is graph based). The most difficult part of migration is related to ontology, the edges. Feature creep is very easy and if you don't set hard limits you can easily find yourself graphing metadata about graph metadata :) You can do this with relational databases as well - recursive logging tables and the like, but it is easier to catch because of the exploding table count. Authorization isn't as easy either, so you'll want to give that some thought before you jump in.