It would be nice if the archive tabs opened adjacent to the source tab instead of going all the way at the end.

Users can save page without login.
Users can save individual links without login.

I see one major bug with Archive this link.

Open source, good integration and future-proof (i.e. easy to add more archiving URLs).

Supports archiving a page to multiple targets with one action.

Easy and straightforward.

Works in Fx48b1.