AnandTech has a review over here. The official performance sheet lists read speeds of up to 1800MB/s, write speeds of up to 1800MB/s, and random 4k read/write performance of up to 220k IOPS. QLC NAND flash memory is slower than TLC but AnandTech judges the performance will be more than good enough for typical users. The disk offers a nice step up in performance over SATA SSDs, at a relatively small price premium:
Given the above caveats and the rarity with which they matter, the 660p's performance seems great for the majority of consumers who have light storage workloads. The 660p usually offers substantially better performance than SATA drives for very little extra cost and with only a small sacrifice in power efficiency. The 660p proves that QLC NAND is a viable option for general-purpose storage, and most users don't need to know or care that the drive is using QLC NAND instead of TLC NAND. The 660p still carries a bit of a price premium over what we would expect a SATA QLC SSD to cost, so it isn't the cheapest consumer SSD on the market, but it has effectively closed the price gap between mainstream SATA and entry-level NVMe drives.The real question is probably how well QLC does over the long run, there's still some skepticism about this but perhaps this is unwarranted.