I tried to use it with a 80,000,000 product database with about 60,000,000 updates a day (edges between sellers and products labeled by price) and it was unusable with the same sizing as a mySQL database that handled it easily.
It seemed great though. Especially since neo4j open source is quite restrictive (clustering is a commercial only feature not available in the OSS version).
That said, I should find out if OrientDB's announced "tenfold" performance increase is enough.
I've had several issues with the "distributed" setup among others.