As with several faster-than-SATA storage upgrades such as Plextor's M6e, the HyperX Predator PCIe SSD is simply an M.2 drive on a x4 PCIe expansion card adapter. M.2 is the socket successor to mSATA. Both are small-form-factor connectors with SATA channels that were created primarily for laptops, but M.2 is also found increasingly on desktop motherboards because of the versatility its four PCIe lanes provides. It can handle fast SSDs, plus a number of different types of peripherals.
But it's only recently that vendors have started shipping M.2/PCIe drives such as the Predator PCIe SSD, Samsung's XP941 and SM951, and others, rather than the older M.2/SATA drives such as the Plextor M6e. It's an important improvement: SATA maxes out at about 600MBps, while an M.2 drive that can use four PCIe lanes has 2GBps (PCIe 2.0) or 4GBps (PCIe 3.0) of bandwidth to play with. The HyperX Predator's controller is PCIe 2.0, so it's capped at 2GBps, but that's still significantly faster than a SATA solution.
The only downside is price: M.2/PCIe drives are twice as fast, but as you can see from the Predator PCIe SSD, significantly more expensive.
Performance
CrystalDiskMark 3.0.4 rated the Predator PCIe SSD at 1,280MBps reading and 1,015MBps writing 4MB sequentially. That's only 17 percent slower than the times posted recently by Intel's new 750 series NVMe SSDs when writing a single large file sequentially. The Predator PCIe also read 512KB files at 720MBps and wrote them at 1,021MBps.
Of course, NVMe has some real advantages, and the Predator PCIe SSD's queued 4KB read and write scores of about 490MBps were only half what the 750 series managed. Overall, the HyperX Predator PCIe SSD is moderately superior to the competing OCZ Revo Drive 350 in pure sequential performance, and quite a bit cheaper.
While a M.2/PCIe solution is pricy, it's easier and more elegant than striping cheaper SATA bus SSDs in RAID 0. You also know you'll get the performance you paid for. When using four drive RAID 0 arrays, I've seen up to 1.4GBps using Intel 730 drives, but as little as 850GBps from other combined drives. Intel apparently has some tricks in its RST technology that it can leverage with its drives.
Recommendations
The 480GB HyperX Predator PCIe SSD's $499 street price is $200 less than the OCZ Revo Drive 350, but costs twice as much as an equivalent-capacity SATA SSD, as well as $100 more than the Intel 750 series. I'd recommend the latter if there were more widespread support for booting from an NVMe drive. If you do have NVMe boot support, the Intel 750 is the one you want.
If your motherboard has an M.2 connector there's also Samsung's new SM951, which is PCIe 3.0 (most M.2 slots are PCIe 2.0, but an increasing number are 3.0) and slightly cheaper than the Predator at the moment. But the SM951 doesn't currently ship with a PCIe adapter card. That leaves the HyperX Predator PCIe SSD as easily (cost considered) your best storage upgrade for non-NVMe/M.2 desktop systems--in other words, just about every mainstream PC in existence.