At first glance the Thecus N4200 might appear to be just an upgrade to a nicer setup display, but once you start peeling back the layers you find that this NAS appliance is more than just a pretty face. The addition of a battery backup module in my mind will be much more beneficial in the long run, giving users peace of mind, all the time.
As a frequent user of NAS appliances and servers I can tell you that having a nice display makes quick configuration changes very easy, but it is a feature used very little outside of the initial setup. For the most part NAS products are set and forget; you set them up and then access the unit from a client PC. Don't get me wrong, the new OLED display is very nice and having it does add to the overall value, functionality and appearance, but when given the option between one of the other features, I will take a BBM any day of the week. Luckily we don't have to choose because Thecus has given us both.
Neither of those two features add to transfer rate performance, but the new Intel Atom dual core processor takes care of that area. The Thecus N4200 is able to deliver files at near attached storage speeds and for many users is the main gauge of how well a unit performs since it is the most often used feature. RAID 5 and RAID 6 require large amounts of memory and draw quite a bit of processing power. The Thecus N4200 has all of the processing power to handle your needs even when RAID 5 and RAID 6 are used.
When it comes to the cost, the Thecus N4200 is at the upper end of the appliance bracket, but it also has the features to justify the cost. Thecus offers many other models if the cost or feature set don't match your needs.