I played it up till the battle with Frank. Like all other games on the native emu, the sound is well off the mark. But it's not TOO bad, actually. To me, anyway. It's bearable.
You need to have frameskip set to 1 (you can try frameskip 2 or 3 for more speed, but prepare for a lot more choppiness). And there is a little garble in the graphics on the edge of the screen when scrolling horizontally. That's not very noticeable, though. The colors seem a little washed out.
With frameskip 1 and at the Dingoo's default clockspeed (336Mhz) it runs a little too slow when just standing still in an empty area of Onnett. In the same conditions at 400Mhz, it runs a little too fast. So you might wanna go somewhere in between there. Iono.
It's a little choppy. That is, the framerate + music are always going a little too fast or a little too slow, dipping up and down slightly and rapidly just moving around the different outside areas of Onnett. I guess you could describe it as being "shaky". Then when you walk into the Onnett Arcade, it's not dipping up and down anymore, but things are moving a little too fast. Then you walk out and fight with Frank, with his fullscreen animated background, and it slows down to like half speed.
It plays better on SNES9x4D (though I didn't test it as much as with native). But don't expect perfection with that, either.
Maybe I'm making it sound worse than it is.
All in all, it seems fairly playable and enjoyable (as far as I know). To me, it is acceptable.