As per Mugen's post, the press seems to be very positive on Vita remote play; imperceptible lag and slight compression
Engadget: There was zero perceptible lag between PlayStation 4 on-screen action and what we were inputting on the Vita. The same sentiment applies to input directly on the Vita for the PS4 game we were playing: no lag, as if Knack were a game being played locally on the Vita.
Gamesradar: During our 10-minute demo we experienced no lag whatsoever. It felt as though we were playing a game running on the hardware, not a game being streamed wirelessly to it
See it here:
Maybe I should dig up some of those posts about how remote play was guaranteed to be notably inferior to a purpose-built device, like a certain other console's.