I bought this to replace a reliable, but aging Netgear ReadyNAS NV+. I was primarily looking for something faster and easy to expand, which the DS412+ is.
The models in this range (412+, 1512+ and higher) all have more powerful processors and more RAM than the cheaper NAS boxes which is where the performance comes from and also allow the NAS more flexibility in running additional applications such as media servers, if that's what you want to do.
First time setup is a little odd since before you can do anything you first have to upload the OS (DSM) to the NAS using the provided Windows software. You also need disks in the unit before you do this so I presume it allocates a small portion of the drive(s) for installing the OS into, not that 200MB is going to matter when you're putting 2TB drives into it.
Once that's done setup is easy and automatic. Allocate an IP and away it goes. The default is to create what Synology call a "Hybrid RAID" volume for easy expansion which the setup does automatically once it's uploaded the OS and formatted the drives.
In use the Synology is _really_ quiet; for all practical purposes it's silent even during drive access. The drive trays have rubber grommets to keep vibration noise from the drives down and the fans are of the large-and-slow-spinning type to keep airflow up without fan noise. There is also plenty of space between the drive bays to help airflow and keep the drives cool.
Performance wise I don't quite get the numbers claimed by the marketing, but it's not far off. On a gigabit LAN with 3 2TB drives in SHR configuration and large (5GB+) files I get a sustained 60-70MB/sec write. Copying folders full of small files (<1mb) sees performance drop to 20-30MB/sec which is not surprising and still more than acceptable.
Email alerts, permissions etc are all catered for as you'd expect on something aimed at the small business end of the market and all in all I'm impressed. My last NAS worked solidly 24/7 for about 5 years. Hopefully this one will do the same!