I'm using elogind solely for its power management capabilities.

Apart from the usual "after X minutes of idle go to sleep" it provides a way
for applications to influence system behavior.

For example my screen locker can lock the screen before sleep, so that when
the laptop lid is closed before the lock timeout, the system won't come back
with an unlocked screen when the lid is opened.
When watching a video or doing a call, sleep can be prevented by the app.
Or I can start a long-running task with "elogind-inhibit" which also prevents
idle sleep.

I don't know of any other software providing these features.