FWIW, I spoke to someone from Micron Technologies, who worked closely on the project, several weeks ago and he did in fact confirm to me that 3dxpoint uses Phase Change memory. Though I am not sure what material exactly, but there's only a handful of possibilities if it is indeed PCM or some slight variation of it.
If you take those kind of statements at face value, XPoint is behind.
Whatever claims Intel made, WD made the claims that their 3D ReRAM has better perf, better costs and much better scaling with production starting in second half 2018.
As for Intel, they said NAND will be profitable in the second half of 2017 and the segment overall in late 2018.This means XPoint would still be bellow break even at that time- so commercially viable only 2019 at best. This is likely also a factor of DRAM pricing. If DRAM prices go back to first half of 2016 levels by then, it puts pressure on XPoint ASPs. NAND pricing can put some pressure on it too.
Intel and Micron are first to market ,that's clear but from a technology point of view, they could very well be far behind. At the very least the point resistion made about costs and scaling does stand, repeating every step for each layer is not exactly the most efficient way to manufacture and scale 3D memory.
3D NAND is TLC, so its reliability is pretty terrible (retention, endurance). 3D XPoint's main advantage is speed (faster than flash but slower than DRAM) but its 3D stacking scheme is much more expensive than that of 3D NAND. 3D XPoint reliability doesn't appear much better than that of 3D NAND either.
Intel is spending a lot of money on NVM. Intel is also the only company losing money in NVM. and they are losing a lot in a one of the best markets in history.
Intel has products out on 3d XPoint. It is clear that the endurance is 5x that of NAND best case (MLC NAND is >3000cycles, SLC >10K cycles). it is also faster than NAND but 10x slower than DRAM. So what is replaces and whether or not Intel has a large lead is debateable. No one expects XPoint to replace 3D NAND
Also Intel continues to sell in SSDs and sell to WDC and Intel sales of component NAND have always been very small.
Summary: Intel is growing the SSD business nicely and introducing fast NAND (Crosspoint) while losing a lot of money.