Yes I have actually. I have used it from userspace for all sorts of things, including crazy things like reading out conntrack state to build network flow visual

Yes I have actually. I have used it from userspace for all sorts of things, including crazy things like reading out conntrack state to build network flow visualisation etc. I have also implemented my own kernel modules that used netlink for userspace communication. I think awesome in kernel terms is always relative. It's awesome compared to ioctl or custom character devices (or the very dirty option of custom syscalls). I suspect io_uring would be a much much nicer alternative but it's also much more modern and not something I have worked with yet.