Lennart Poettering has written a guide for optimizing systemd to the extent that a two-second boot-time or less for this popular free software project.
The systemd optimization guide can be found on the FreeDesktop.org Wiki
While right now there's many manual steps to lower the systemd-controlled boot-time, the goal is to eventually incorporate these tweaks into upstream distributions as the defaults. "It is our intention to optimize the upstream distributions by default (in particular Fedora) so that these optimizations won't be necessary. However, this will take some time, especially since making these changes is often not trivial when the general purpose usefulness cannot be compromised."