Great, when it works
I flew SYD-PER-SYD over the weekend and had mixed success using Passbook.
The SYD-PER check-in on my mobile worked a charm and the boarding pass loaded into my passbook as described in other posts above. Was was weird though was when I scanned my Passbook when boarding, a printer spat out a small chit with my name, flight and seat details, and my status. The agent then handed it to me so that I could show it to the cabin crew. What's the point of going paperless when the process generates paper?!?
The PER-SYD check-in did not work at all. I couldn't get past one of the screens because it said I had to correct the highlighted error. There was no error highlighted on the page, at least none I could see.
I tried checking-in again from the beginning a couple of times, but with the same result. In the end I checked-in in from my iPhone using the full web site. There is no way on the full web site to send the boarding pass the a mobile device, which seems short sighted of Virgin.
Agents are unable to send boarding passes to mobile devices, which again I think is short sighted.
Also, if you try to change your seat assignment while checking in on the iPhone app, there is no back button to return to the previous screen without choosing a seat. The only option is to start again from the beginning.
There are some serious usability issues that Virgin needs to iron out with their app and with mobile boarding passes before this process is seamless.