The PS4 - Vita combination is great.
I tried it out yesterday for a bit.
- played Resogun - played well, did not notice lag problems.
- played freeking War Thunder on the PS Vita, although R2 is mapped to the back and I wasn't able to shoot shit when in a plane. It would be super to map mouse aiming to the back trackpad and move a couple of buttons to the touchscreen, but they don't have specific remote play support I think
- but Warframe does have remote play control configuration option. Awesome. But that one I got to try for a couple of minutes only.
Preliminary conclusion: AWESOME!