I'm having difficulty visualising the advantages over normal a FS?
Currently, a journalling filesystem is the holy grail of filesystem design.
I can't find an explanatory URL so here goes:
The basic idea is, in theory, increased data integrity in the case of disaster. Say for example the machine crashes during a write operation, the idea of the "journalling" is a database-type setup, where you keep a record of the old data/transactions, and allow rollback to old data if there is a need.
I don't think performance is an advantage. I think developers are hoping to equal modern FS performance.
Come to think of it, what's the point for WinNTx, NTFS is pretty damn good already.