Watching this PlayStation ad, it really sunk in for me: it's one thing to hear about the ability to play/stream PlayStation 4 games remotely on your Vita, should you own one. It's another thing entirely to see that feature in action and realise, holy crap, it's like I have a portable PlayStation 4 in my hands.
Oh, there's other stuff in here too -- the interface, the sharing, stuff like that. All good features, but personally, none as impressive as remote play. Although it's worth noting that it may not actually work as well as shown here (Stephen notes that remote play on the PS3 wasn't the most reliable thing for him), but one can hope, right?