I'd personally say a distro-agnostic user guide for Cinnamon, only because almost everything else is covered in the normal Mint user guide. I'm being a little bit selfish though, as I run Debian-based stuff instead of Ubuntu.
If it were to be distro agnostic, then it might be good to include details from the download page: http://cinnamon.linuxmint.com/?page_id=61
. I would add that in LMDE you can use the Mint repo to install it and there is a cinnamon package in Sid that is currently the newest version.
Edit: Forgot to include the debian packages link: http://packages.debian.org/search?suite=all&arch=any&searchon=names&keywords=cinnamon
. It's still missing nemo, but otherwise it works and is up to date (1.6.7-1).
Dell XPS 15 l502x - Debian Testing 64-bit NetInst Xfce, SolydX 64-bit Debian Testing, SolydK 64-bit SolydXK Testing
Old Gateway Pentium 4 Desktop - Arch Linux 64-bit Xfce and SolydX 32-bit Sid