This will be obsolete once the 11-46T XT cassette is released later this
summer, no? New XT will be lighter (as Shimano stated "The CS-M8000 has a
target weight of 450g") and it will also presumably be cheaper to get the XT
11-46 than an 11-42 cassette + wolf tooth 45t ring.
Looks cool, can't find any demo video using Google. Should be pretty neat, if
they can come in around $350, for similar or superior quality, I think that
they could put a pretty significant dent in GoPro's market.