Asustor's AS5108T hits high marks in almost every category. It's available at a range of price points, depending on the seller you trust to buy from. We found the AS5108T for less than $800 and up to almost $1100. Assuming you're looking at the lower end of that scale, the system represents an excellent value compared to nearly every other eight-bay appliance. We'd especially like to see how it does against QNAP's TS-851; the two sport similar specifications and features.
QNAP and Asustor lead the market in software features. The former's products introduce a lot of enterprise-oriented capabilities to lower-cost hardware. The latter takes a more client-focused approach, implementing those features really well.
The ADM operating system is easy to work with and ties into the platform really well. Most NAS companies have moved over to the Web 2.0 look. But Asustor was the first. Most of the competition followed suit because the layout, drag-and-drop icon placement and overall experience make the OS more user-friendly.
Performance wise, Asustor's Linux-based Data Master operating system utilizes the hardware to its fullest potential. Even with just 2GB of RAM, the AS5108T keeps pace with appliances sporting more powerful SoCs. The limited system memory can become an issue once you start loading up lots of applications. Fortunately, there's always the option to add more through a second slot. That's an upgrade we'd highly recommend.
Update: Asustor released ADM 2.5 after we finished this review. We tested with version 2.4. One of the new features in version 2.5 is the inclusion of SMB 3.0.