TL/DR: Perfect amplifier if better than stock sound and ease of installation are your goals.
I've installed this on a Gameboy Color that I've been repairing. I've also used the RetroSix CleanAmp v1.2 so my comparison will be between this amplifier, the CleanAmp, and the original.
In terms of installation this amplifier is far and away the easier solution. The solder points easily match up to the locations on the board they need to and it is a simple and straight forward process to get it installed.
For the audio quality it is noticeably louder than the original audio setup. It sounds good and in my opinion is loud enough for what I am wanting out of a Gameboy.
Now I have installed it along with a Funnyplaying IPS and button LED kit without yet installing any kind of power modifications so my next few statements are more than likely related to power issues due to my install rather than flaws in the amplifier itself. Having said all of that I have noticed a significant amount of hum and buzz from the speaker even when it is at minimum volume. It also doesn't seem to be as loud as the CleanAmp amplifier. But again I want to say that I haven't yet installed and upgrades for power which I feel would fix both of those issues.
I will hopefully remember to update this review after I get a power solution installed and see how that affects the audio.