On a scale of 1 to 10, I would rate Qnap a 20. It's so amazing. I was actually choosing between this Qnap and Synology but I'm glad I got this Qnap.
Setup is a breeze. And although this is just an entry level model (TS-220), there are tons of useful features on it plus the expand-ability is great, too. It has 2 USB 3.0 ports and 2 eSATA ports where you can connect additional external drives and access them anytime, anywhere in the world. It has a "Linux-like" web interface with very useful apps. It also has apps for iOS and Android where you can download, upload or save files to and from the NAS even when you are outside your home network.
The QSync feature is a good one too. It syncs your files across all your PCs so that you have all your important files available to all your PCs and gets updated automatically when you edit a file from any PC. I have the 2 main hard drives on RAID 1 mode for all my important data. The external drives contains all my movies, photos, music, etc,. Transfer speed within my network is between 40Mbps and 90Mbps depending on the type of hard drive.
Here's the desktop/web interface:
And here are some Android apps shots: