I have used it only 3 times, it is very good, it does its job well. It is worth its money.

After quite a bit of searching, I ended up with this. I wanted to remove a stuck Allen screw with a stripped head (it had become completely round) from a part without damaging it, and the head had to be notched so the screw could be removed with a screwdriver. The job was done in a few minutes! It engraves and cuts metals perfectly, always depending on the size and thickness. Also, the heads for engraving, carving, and sanding for various materials were a lifesaver for me because I deal with 3D printing and all these are extremely helpful tools. It also drills soft materials (wood, synthetics, melamine, plywood, etc.) with ease, always depending on the thickness and dimensions of the material. For 30 euros, I don't think there is a better value for money.

I used it to clean the grout from the tiles that had tile adhesive... although I have never used something similar before, it served me just fine

The positive aspect of this specific speed bike is that its low price is below average in terms of build quality and functionality

It is a very practical tool at a good price. I have used it for various small tasks and it helped me. My opinion is that it is worth its minutes.

Without having any particular knowledge, it seems honest.
I don't know about (nor do I have anything to compare) the quality of the tips, but the tip that screws on top of the discs, etc. was not completely straight for me, so the discs had a fairly noticeable tilt, even more noticeable due to uneven wear on the top and bottom sides.
It was corrected to some extent (not completely, but I didn't bother, just wanted to see if the idea would work) by using it without the tip and holding it vertically (by eye) on sandpaper.
Anyway, it did the job I wanted, to scratch some worn screws.