I've only run mic in with P48. There was some discussion in another thread that the front end on this thing is a common path and that line mode isn't really switching anything out of the signal path. The only difference then between the two modes would be the input impedence.
So if you do try the V2, please post your impressions. With the V2 being transparent and the 722 gain stage possibly not switched out, I want to know if you hear any difference.
You should check your firmware even if you haven't seen any problems. If you are running 1.24, you really need to get it off there. SD said there is a bug in there causing buffer overrun problems that explain the media slow errors, the lost data, disk full, etc.
It is a nice box. It did a great job on the mule show in Charlottesville.