Pros: Basically plug and play...plug in the esata cable and go to the management software and set it up. Put in 5 WD RE4 2 TB and in a few hours it all set up. Used this to expand a 1812+ 8 bay nas by synology.
Summary: I have yet to finalise my NAS configuration in my office - between the needs to store CCTV footage, work files and archiving. What's great is that the unit can be part of seamless expansion of 1813+ or standalone volume. The other plus point is that we also own the Synology DS713+ DiskStation at home, which means that if the unit is no longer needed at work it can be utilised in the same way in the home environment. So for us all bases seems to be covered.
Summary: Bought this to expand my Synology 1812+ after weeks of deliberating. I found it easy to set-up and use. Integrates with the 1812+ really well. Basically there are two options to use the DX513 expansion unit - as a separate volume (which can be set as a RAID enabled volume), or as a seamless expansion to the original volume on the NAS (in my case the 1812+). I rate Synology products very highly, and the concept of the DX513 is great.