Generally, it's satisfactorily well-made. But,
1. The front mats slide around. Bit concerned will interfere with brake/accelerator pedals. Would be good if design improved to make it stay in place.
2. Since it's flat/2D, it won't cover any bump/raised areas if the car floor is not flat. Would be great if the design can still cover most of the raised areas by being bigger. Don't mind if small curves not covered, but at least majority covered.
3. For specifically the MX-5, since the boot is small...