I've just tested with mine, attached to a Mac with latest version of Mac OS and it gives me 260MB/s for, both, writing and reading. I've tested with the default settings (block size, etc.) for BlackMagic Disk Speed Test.
It is not a NAS, so one PC connectivity at a time. You need to format it with compatible for both Mac and Win if you want to share content just like any other external disk (eg. USB hard disks).