After running some tests I was ready to deploy to a new production server, but unfortunately my hosting provider (OVH) doesn't offer a ready made image.
After trying to use Debian as a starting point, and several failed boots, I threw in the towel... Seems like OVH does funky things with their EFI which doesn't work without some black magic.
For now I'll continue using it on my laptop but it's not living up to its full potential, most of the configuration is for desktop stuff and NixOS doesn't really cover that.
When I get the chance I'd really like to try it on my servers, hopefully sooner rather than later. I can see it working really well with Saltstack for infrastructure management.