I tried a few games and they all seem hard to play since they go as far as having 7 frames of lag. Ultimate Ghost and Goblins is practically unplayable since the game itself is hard enough. Same thing with the Metal Slug games. I think the fastest game with the lowest input lag was LittleBigPlanet with 4-5 frames of lag (which is still high). This places the PPSSPP core at the top spot of the slowest cores, beating Mednafen Saturn even.
I tested this with GPU sync ON and zero frames on a CRT monitor. That makes it the optimal, fastest possible setting outside using frame advance. I don’t even want to know how bad it will be on a LCD.
What i do want to know is if this is a known problem with PPSSPP in general. At this state, you can’t play most games on it IMO.