The WD 2TB RED comes with me in a Synology DS213 + is used. Before that I had there a WD Green 1TB indoors which is significantly louder than the RED. Do not regret my decision and soon comes another 2 into the same NAS to.
UPDATE 04/12/2013: After more 8 months of continuous use in the NAS drive that runs 24/7, I can say - all good. Runs still clean and I am still very satisfied!