First things first: we really thought that a phone of such size would be a stretch -- both figuratively and literally. But when we picked up the device, it felt surprisingly comfortable to hold and much lighter that you might anticipate. As for the design, make no mistake, Samsung merely took the Galaxy S 4, and gave it a good zap with the enlargo-gun. The curves, the home button, the bezel are all taken from its little sibling. The color scheme, too, was lifted directly from the GS 4, with the models on display sporting the same blue chequered pattern.
What clearly isn't the same is that screen. Not just because it's so much bigger, but because (much to our chagrin) it's a lower resolution, to boot. The "HD" screen -- in the short time we spent with it -- didn't actually look bad. Of course, this was just a few moments under the bright, possibly flattering conditions of Samsung's controlled display environment. The real acid test will come when we get to put it through its paces in a proper review.
As for general performance, again, we found it nimble enough while navigating menus and TouchWiz (there's Android 4.2 underneath). The 1.7GHz processor might not have the pure might of the two Galaxy S 4 processor variants, but it handled the demo videos, browsing and other material as adequately as you might expect. Most of all, however, we come back to where we started: the sheer size of the thing. Samsung was keen to describe it as large but comfortable -- pocketable, even. And that it is. But is that enough for it to win the hearts of the masses? It's hard to tell at this stage, but stranger things have happened.
Update: As you watch the video below, note corrections on a couple of the specs -- this 6.3-inch version has a 720p HD screen, not qHD like the smaller 5.8-inch phone, and while the demo unit wouldn't open up it does have a removable battery.