I did watch the YouTube clips you posted, and they really are intriguing! I'd kind of like to TRY them. Maybe I'll try to get a set of the greytones and do some greytone "coloring" to get a feel for them. If they're really just India ink, then it'd be really interesting to try them on a nice thick paper and have a brush and some water standing ready nearby, to see if basically it would be like painting with ink, only a bit more contained.
I also like that they DO come in a variety of tips, although my impression so far is that the largest color selection does not come in the brush tip? But maybe it's just that the largest color selection doesn't come in the BIG brush tip, but comes in the regular brush tip.
What surprised me, though, is that they don't look all that much less expensive than Copics, and so it seems to me that the biggest drawback with them is that unlike Copics, they aren't refillable. So in the long run, they aren't as cost-effective. And you would have to have back-ups of all of your most-used colors ready, in case you ran dry in the middle of something. (I have to have back-up refills of all my most-used Copic colors, but at least one bottle of the refills is good for like 8-12 refills of the original pen, so it's like having 8-12 backup pens, for $5.)