I really love these Merus amps. There is something different about them compared to typical class D amp with 2 power states only to modulate the analog signal. With the Merus you have 3 to 5 different power states, this makes the modulation and transition smoother, closer to class AB. A similar effect as on a DAC which have more "Resolution" (16bit/48kHz vs 32bit/384kHz) to reconstruct the analog signal.
The problem with some of the Merus amps is that some manufacturers used TL072c or NE5532 opamps on them. This is clearly a mistake as the amp could take full advantage of using a modern opamp like OPA1656 or OPA1678. Sadly these opamps are soldered to the board and replacing them requires some "nerves/balls".
The other issue with these amps is tat some manufacturers did not add the right output filtering, some did not add chokes/inductors on the output. I understand they might not needed by the most of speakers, but if you try to bi-amp a speaker you will have problems with the tweeters because they don't have enough inductance and don't act as the right filters.
The other big problem is when you try to measure these amp without the output chokes. The measurements might you believe this is not a good amp, and this could not be far from the truth. You just need the right filtering to measure it properly. Like what happened to Amir with the SMSL A100, he saw a lot of high frequency distortion because of the lack of filtering, so all those 10kHz and beyond distortions could be eliminated by using the right filtering.