The real power in Real Preview is the versioning system. This is something that has been missing and sorely needed. No more having to explain to a client that there is no undo once you save or apply changes. No more having to run Akeeba backups constantly just to make simple edits. And no more having to explain why the preview button is "broken".
Real Preview is simple to use and understand. The interface is very intuitive for any Joomla user. It couldn't be any easier to use. I haven't needed support though I did send in a question that was promptly answered within the hour.
They are planning K2 support in the near future as an added bonus. This will definitely be a must have for all of our Joomla installs.