For me at least given 30 years of IT experience it wasn't hard to setup and get working (the interface wasn't reliable from a web browser on a phone you have to use a desktop PC) but if you're an average non-technical end user I don't think that you should purchase a NAS device. You will end up getting someone to install it and set it up for you.
The functionality of the NAS device is excellent and will do things that even a business would want. The device would be more accessible if there was an express/home setup option so it would disable snapshots and set it up with all of the storage automatically and provide details on how to map drives or access DNLA/uPNP functionality. While I will end up using things like iSCSI most people will never use any of the advanced features.
It's 5 stars because what it does it does really well it's just that the device is not for everyone. The admin interface is easy to use but if you don't know a lot about what you're doing it will be hard to setup.