Not impressed. They once said 5X could hit nearly 16 as well and easily 14. Not much of an improvement.
Also still the issue of consuming more power than HBM, and even with HBMs interposer, it still takes up less space than a GDDR layout. Not to forget that HBM/2 standard speed is 512GB/s, when in fact it is capable of 1TB/s. GDDR just seems like it's dying now.
By the time it's mainstream, HBM2 will be pretty cheap and probably 3 on the way.
Although good to them on trying. Always nice to have options, just don't think this will be the highest performance option available