Solaris had an init system like systemd for some years, called SMF. It was first released in 2005, the same year Apple released launchd.
It features service dependencies, log collection, fault detection and much more. One of the biggest differences is probably the usage of config files. SMF uses XML files to describe the service and its variables and a program called svcprop to edit variables and create new instances of the service. These can then be managed with svcadm.
HSTORE still is only storing key, value pairs. Nested HSTORE is something we might get in 9.4. JSON/V8 does allow nesting but doesn't allow indexes for arbitrary value access - something that MongoDB easily does.
So depending on your use-case and the type of documents and queries you are dealing with, neither the current HSTORE implementation nor the current JSON implementation will work for you, while MongoDB's model might.
But the reverse is true too: Some use-cases are highly relational and it would be really painful to do that with MongoDB due to the lack of easy joins (you have to do them in your application logic which means a lot more work as your requirements change).
Pick the right tool for the job.
Me personally, I prefer the immense flexibility for querying a relational data set over the flexibility of not having to deal with schemas. The reason is that it's much easier to change or add an SQL query than it is to re-format and re-duplicate all of my data followed by more or less manually implementing as good query plan in application code whenever the requirements change.
ZFS uses block-level checksumming for every block. The auto healing can be used when there is a second copy or another way to rebuild that block, read Raid-Z. So you get the auto healing already when using mirror.