I have not had the opportunity to use it, but have watched videos of this and several others in action.
First it will only work well for cylindrical objects, such as a can or glass with substantially parallel sides. Anything with a conical cross section will require some sort of adapter so both ends have the same circumference. It's up to you to provide the adapter. Competitive models have conical end-pieces to capture the object regardless of the diameter of the respective ends, and it is the end pieces that are driven, not the rotating supports. Engraving something spherical will be almost impossible.
Second, in order to place something under the laser, the entire engraving assembly, laser and all, must be lifted up by the height of the Rotaroty tool, plus the diameter of the piece. Again your method of lifting is up to you. Competitive models have the laser unit as part of the entire assembly, not as part of a separate assembly. Yes they are more expensive as a result.
While the design is pleasingly simple, I find it will be limited in application, and frustratingly require cutting something to raise the whole platform for whatever item I am engraving.