The syscall translation makes it more useful than the previous UNIX subsystem, because it means it can near-perfectly emulate a popular POSIX-like system (Linux), and thus be compatible with most of its software, rather than being its own eccentric platform that existing POSIX software must first be ported to.
I don't see the value if it's not more stable than "excentric" platforms like Cygwin and MSYS, but I guess I wouldn't use it either way because there's no way I'm installing Windows 10 on my hardware.
