If it were sold without its tablet dock, you might give the Padfone phone a second look all on its own. It's really pretty, after using it for a few minutes, it's just as powerful and smooth as any other flagship Android phone coming out, like the Optimus G Pro or the HTC One.
The phone is fast. Every app loaded up and opened like lightning, though the selection was limited due to lack of a connection on the demo units. But it was smooth, and there was no stutter despite Asus' considerable modifications to Android (it's built on 4.1.2). The screen is just as beautiful as you'd expect given the absurd resolution, but the thing that stands out about it is its vibrant colour performance. It's just so bright and saturated (it didn't seem overly saturated, but we didn't have time to load up pre-shot photos) that it catches your eye, even under hot display lights.
It's also relatively light, and doesn't feel its 5-inch size. It's sort of like the Droid DNA, in that it's huge, yes, but feels somehow less huge than its 5-inch contemporaries. The aluminium build is fairly nice, not top-tier industrial design nice, but ahead of the curve. It's sort of reminiscent of an iPhone 4 crossed with a Zenbook.
The tablet portion of the Padfone is manageable, and not as unwieldy as it could be. It's not as comfortable to hold as a Nexus 10 or an iPad, but still fine for handling as a tablet. We weren't able to get any content loaded up to try reading articles or books, but it seems like it would be adequate, though not ideal. The 16:10 ratio on it is decent for holding in portrait, but the phone being on one side in that alignment limits how much you might use it like that.
As for the switching, it was pretty seamless. There's a second or two of hiccup, but it's nothing that worries you as you switch from one device to the other. It's faster than the time it takes to load a second display after plugging it into your laptop, for example. There was no perceptible slowdown going from the phone to the tablet, either, but again, we didn't have access to the really graphically or processor-dependent apps. But given its impressive guts, it would make sense for the performance to be that smooth.
It's really pretty impressive.