I got some of this in. This is all preliminary as I've only played a couple of hours using it.
This clearly isn't a substitute for Kamui. It doesn't "paint" on like Kamui and it clearly is much harder. It does seem to be finer grit that Master, Blue Diamond, etc.. If it lasts longer than Blue Diamond, it isn't a significant amount and doesn't seem to compare to Kamui at all.
My main point here is if you are thinking this is Kamui for $2 per cube (ok, octagon), it clearly isn't. However, it appears to be very good chalk and for those who don't like Kamui but prefer a more traditional chalk, this may be worth trying.