Thought I'd chime in
Bought my first Synology product: DS411j
I went with four of the Hitachi 5K3000 3TB 5400rpm drives due to their impressively low price.
Despite that particular drive not being on the compatibility list when I bought them, I took a small gamble anyway.
I haven't tried every single feature (there are a lot of them!) that the DS411j offers, but so far, the Hitachi 5K3000 3TB drives have worked without any problems. All four show up perfectly as 2.79TB drives and I haven't noticed a single issue setting up the NAS or transfering files to and fro.
The drives and NAS both run quiet and cool, which is excellent. Obviously, the DS411j and these 5400rpm drives are not going to be the fastest NAS out there, but for my purposes, I'm not really concerned with top-level speed - I just need the space!
For the low price and high capacity, these Hitachi drives were perfect for me. I've already nearly filled the 12TB capacity so I feel very confident in purchasing a second DS411j and four more of these 5K3000 3TB drives in the near future.