Is the PSTV gud as a standalone console?
It's ok. I wouldn't go as far as good.
Not every Vita/PSP game is compatible. Pretty much all games that rely on touch controls won't work. This knocks out some of the Vita's iconic games like Gravity Rush, which would have been a blast to play on TV.
Even stuff that doesn't rely on touch screen functionality doesn't work like the Netflix app. It's available to download from the PSN shop, and the hardware is supposedly exactly the same as the vita, but the app straight up doesn't work.
The ones that do work, work well though. I'm currently playing Persona 4 Golden and Velocity 2 atm and they play perfectly with my spare PS3 controller. VitaTV can only output at most 720p though, so be weary of that. I was expecting that going in, so I wasn't shocked when I saw the games rendered on my TV.
Honestly, I can only recommended it to a very specific niche user. A user who, either already has a collection VitaTV compatible vita/psp games that they never play on the handheld, or a PS4 owner looking to stream to another TV in their home and who is interested in some Vita titles as well.
I personally, only bought it because I fit one of those conditions and there was a boxing day sale, selling the system for $60. I have a hard time recommending it at full price.