The price is high, so the product is aimed at hardcore retro gamers who want the ultimate in console graphics. I tried it on Dreamcast & GameCube, and the results are simply amazing. It delivers exactly what it promises.

Two notes: I didn't try it on an older 2D console, but I have a feeling that in this case, the OSSC might be a better solution. The strength of the mClassic lies in its 3D graphics. The second note is that the input is HDMI, so unless the console has an HDMI output, you will need either an HDMI converter or connect the console's output to the OSSC and then connect the OSSC to the mClassic (and from the mClassic, connect it to the TV). In my case, where the consoles didn't have an HDMI port, the OSSC provided better and more vibrant colors than the HDMI converter.

Good build quality. It does what it promises. Essentially smooths out textures, gives a nice depth of field effect for graphics-weak consoles like the Switch, and overall makes the image more enjoyable. There are many related comparison videos on YouTube. Now, whether it's worth the approximately 125 euros it costs, that's up to each person's pocket. If someone is looking for detail, has invested in the Switch, spends time with it on the dock, and has the budget, they should go for it.
Because it is a tool that improves the image, one should not expect it to be an "external graphics card" because they will be disappointed. It does not improve console performance and does not add frames.
5 stars because it is the best at what it is intended to do.