@CV643D
The biggest advantage is that its a cheap chip, so it won't add much to the cost of the board, so "why not". Since it IS a cheap chip, and any task you get it to do will likely be parallelised, you can scale up your process by throwing more cheap xmos chips at it via the xorro slot for an instant gain.
On the other hand, one nifty thing it could do is provide a Catweasel like floppy controller with nothing more than a passive adaptor from the xorro slot to standard floppy connector, for example.