Good idea, bad execution - as it stands, the phone is based on under-performing hard ware. However, if a larger, mainstream manufacturer produced a 4g, dual core, 1.2ghz hummingbird version capable of supporting the mult-tasking on both screens and re-designed the screens to be edgeless, 4 inch screens the result could be a "tablet-phone cross breed" similar to the Dell Streak that has better multi-tasking capability and be a closer bridge to the 7 inch e-reader style tablets with more pocketability.
As an idea, I think it has more potential than the dual screen tablets, because it retains the functionality of both the phone and the tablet by trading off thickness and batterylife (which should be manageable considering the phone is functional with 1 screen.)
