I do have one. Really nice portable option. I haven't tried rolling the opamps yet, but so good so far. The volume pot is really smooth with a nice tick when it switches the device on. The build quality is very good. My only concern is batteries connectors, but the can be swapped pretty easily, so it isn't much.
In terms of sound and power it is really a thing given its size. With stock JRC 4556AD the sound is very-very decent. No peaks, very clear and smooth.
Anyway, given the price there is no flaws at all =D
If you live somewhere not so far away from Indonesia this might be the best starter amp for you. Rollable amps, decent output, clean sound with no hiss(at least for 16 and 32Ohm IEMs that I tried, have no lower impedance models) - all of that for 30 USD is really a nice deal.
PS- Keep in mind that you will need to get interconnector separetely (many DAP come with one, so it isn't a big deal).