As I understand it, you get 10% experience boost rested bonus. It's also a way to push time forward and wait for vendor stock changes which is why you can change the sleep time to X hours. As you say, you get some healing too.
It can also be used as a way to speed up time on planets where time passes faster. Venus is an example of this where 24 hours in Venus time is a huge amount in Earth time. I think you can use this method for collecting larger amounts of resources you are gathering at outposts quickly as time is accelerated even more.