Lite Mode, according to the patch notes, will allow the PS4 Pro to improve the frame rates up to a maximum of 60 FPS. This means the game will try to adjust rates while everything's running -- it's certainly not going to run at a consistent 60 frames each second. (Courtesy of Digital Foundry, you can see how this works in practice, above.)

Early impressions are mixed: some users on this Neogaf thread suggest the transition between different frame rates is particularly jarring. This update hasn't affected the "high' mode, so there's still some choice for Pro users. Howver, the original fixed 30 FPS "lite" setting has unfortunately disappeared: it's not as smooth as it used to be.

But hey, you also get some Nier soundtracks added to your in-car playlist: it's definitely not all bad.