Although it packs the same amount of cores and threads as the US $499 priced non-HEDT Ryzen 7 1800X, the Threadripper 1900X brings plenty of benefits, including the quad-channel DDR4 memory support as well as a total of 64 PCIe lanes.
In case you missed it earlier, the Ryzen Threadripper 1900X works at 3.8GHz base and 4.0GHz Turbo clock and uses the same TR4 socket as the rest of the lineup, meaning it will fit in AMD's X399 chipset motherboards. According to AMD, the Threadripper 1900X will be using a so-called "4-0-4-0 diagonal configuration", which means that only two CCXs have been enabled, leaving it with 8-cores and 16MB of L3 cache but also access to full quad-channel memory interface and all 64 PCIe lanes.
AMD places the Threadripper 1900X against Intel's Core i7-7820X, which has the same amount of cores but offers less cache, and a whole lot fewer PCIe lanes.
AMD also announced that the NVMe RAID support on X399 chipset motherboards will be coming on September 25. The software and BIOS update will be bringing bootable RAID 0, RAID 1 and RAID 10 with support for up to ten NVMe drives. Unfortunately, the same support won't be coming to Ryzen X370/B350 motherboards, so it will remain reserved for Threadripper HEDT lineup.
According to AMD's own performance slides, the Ryzen Threadripper 1900X should not be that much faster than the Ryzen 1800X, and it does not make sense unless you really need those 64 PCIe lanes and depend on NVMe RAID support. Even AMD lists a few specific usage models, which include a rendering powerhouse and deep learning, where PCIe connectivity does matter.
In any case, AMD is definitely putting a lot of pressure on Intel's HEDT lineup and the Ryzen Threadripper is still the cheapest HEDT CPU on the market.