I think the best part of this product is the fact that you're being sold an overpriced mechanical pencil in fancy looking cardboard. I'm not even mad, it's so clever.
Note that I did not receive the "Premium" scribing set, but rather just the "starter kit" which is a smaller box without the Master Guide 2.0 tape, but the important bits are the pencil and the "chisel". The tool is worth the price, especially if your aim is to deepen existing panel lines.
I'm near-sighted, but I can't see the face of the chisel, because it's *tiny*, like a mechanical pencil lead and that's exactly how it works. However, if you look at it under a magnifying glass, you can see a tapered four sided tip that gets narrower and ends in a tiny square with sharp edges.
If you break this tip, there's no more "lead" to use no matter how much you click, that's it, it's gone. Luckily, it seems fairly sturdy and is likely made of carbon tool steel, retaining a tiny bit of flex while also being sharp (don't bend it, just pull it along and let it do its job).
The mechanical pencil is really just a standard mechanical pencil, even the cap comes off... But, the clever part about it is that the entire tip closes with a deep click, so your chisel is safe inside, while soft clicks extend and allow you to push in the chisel.
The chisel is "multi-directional" not omni-directional, working best in a North, East, South West kind of directions, while going diagonal will have the tool chatter a little, causing uneven drags.
Preferably you're supposed to drag it along one of the flat sides, but because you literally can't see the facing of it, you just... feel your way with it, or just don't think about it too much. Put it in a panel line, pull it along the groove or pattern and just chisel away letting the sharp edges do the work.
You can also drag it along scribing tape for a guide line, though the tip might veer off, due to the square tip, so just be careful and pull slightly in towards the tape.
If you for some reason want to freehand scribing (you crazed monster) I'd recommend using a DSPIAE carving needle instead.
Bottom line, is this worth the money? If you really just want to deepen annoying shallow panel lines, I think this is probably your best tip-and-holder in one with that 0.15-0.2mm width, which is good for both HG and MG kits.
It's versatile, it's somewhat beginner friendly (I'm a beginner, I'm friendly with it despite it stabbing my finger), so in that regard I'm happy. For an experienced scriber, you probably have line engravers and other tools in different widths, so this might be superfluous. If you think the price is steep, that's fair, you can probably make due by filing a needle flat and giving it an edge or two with a sander.
It's possible to get replacement chisels from Gunprimer, but the price is supposedly steep. The chisel really is what you're paying for, the cheap mechanical pencil, albeit useful, really isn't anything special.