>>5893778I bought packs of 10 each of the Zebra G-pen, maru, and tama nibs, as well as the pen holder so here's my actual user opinion:
The holder is good, no complaints besides it being a little more finicky with western nibs like the Speedballs
The G-Pen isn't all that good, it's hard to clean because of the curves and doesn't perform as well as my Speedball and is in a weird zone where it's too flexible for a pen and not flexible enough to warrant using it over a brush or a harder nib
The Maru pens are fine, I feel like they might scratch a bit more than the Hunt 102s but it's a perfectly good mapping nib and cheaper to find (for me at least) in bulk
The Tama pens are my favourite of the bunch, they're like the Hunt 512 (which is my favourite nib I've worked with so far) but like the Maru pen much easier to find for me
That said I've largely switched to brush pens for most of my inking (also Zebra actually, the super fine pens are cheap as fuck and really good for what you pay for)