Fact is, the games on the PSN pretty much carried the Vita for quite some time, and some would argue that they still continue to do so. At launch, however, there was no question about it, as overall, the quality and price of the games made the full retail games seem insignificant. In fact, Sony must have thought the same thing, as just a few months after its release, they put a few of biggest retail launch games up for free for PS+ members, including that Uncharted: Golden Abyss game.
One of the downloadable PSN titles available at launch was Escape Plan, a quirky black-and-white puzzle game that didn't get nearly the hype it deserved. It was great, it was easy to get in to and enjoy and had charm oozing out from every corner, in a very dark and disturbing way. When it was first released, however, the developers tried to force all the unique Vita features like the rear touchpad and such as controls for the game, and they weren't an option. Instead of putting a spotlight on the cool things the Vita could do, they made everything feel like a gimmick which only made the controls frustrating at best. Eventually they got the picture, and patched the game to add button support as control option, which opened up the game substantially.
They also released a few pieces of DLC, but unlike most developers, they didn't aim to make as much money as possible right off the bat. One of the DLC packs was only a couple of pennies for the first day, and another one was about half a buck, if I remember correctly. The prices have sense gone up to normal DLC prices, but they wanted to thank all the early adopters of the game, which of course was greatly appreciated.
I haven't put much thought into the game since then, however, as so many other games have graced my life that I just haven't even had time to think about it, I haven't missed anything though, as they went silent for quite some time. Well, to my surprise, the developers were actually working on a PS4 port of the game, which was just released completely under the radar. Best thing about it, is they gave it away for free to everyone who already owned the Vita version, including all the DLC. They did give it its own trophy list, however, unlike Sound Shapes, which means that you'll have to play it all over again to earn those trophies.
Don't fret, though, as the game is just as good and fun as the Vita version was. Same game, just with a nice polish on it. Nothing is different that I can tell, which isn't a bad thing considering it was free. The only thing about it is that they implemented a few touch controls to take advantage of the touchpad on the DualShock 4 control, and why they are a little finicky and cumbersome at time, they aren't too prevalent and probably won't keep you from completing a level with three stars, once you get used to them.
Now, the only thing I haven't tried is to play the PS4 version of Escape Plan via Remote Play with my Vita, essentially creating an Escape Plan inception or black hole. I might literally crash my entire Sony network of systems if I try it, but the more I think about it, the more curious I am. If you don't hear from me again, send help. Just not via the PSN.