I haven't. I was trying to use nixos-generators, because at some point I want to generate a custom, stripped down image of NixOS. But until then, I might use nixos-infect, if it gets me a running instance of DO quicker.
It's super easy and works every time. You might want to change NIX_CHANNEL=nixos-19.09 to NIX_CHANNEL=nixos-20.03 since 19.09 is the previous stable version. I use nixos-infect along with Morph so I don't care about the custom images that much - a fresh/bare NixOS is all I need to build, push and deploy the actual configuration through Morph.