It might come pre-formatted, I would at least do a Quick Format just to make sure it's working. You don't have to these days, but I usually do a full format and error check on new hard drives, especially the big ones, to check out the drive before use. Since computer components seem most likely to fail soon after being put into use, I use the crap out of the drive for the first few days to make sure that if it is going to fail, it dies within the refund/return/exchange window from the vendor to avoid warranty hassles.
I scrutinized "the Reds" before buying 4x 2TB NAS drives two years ago. Despite the rumors and disparagement, I chose the Seagate NAS 2TB drives. Haven't had a problem with any of them. The Reds are also probably "up-to-snuff."
OEM-wrap bare drives should not arrive pre-formatted, although it's always possible while I've never seen it.
Here's what I'd do for staying within whatever 30-day RMA deadline you have for a new purchase.
1) Format the drive -- and uncheck "Quick Format." Yes -- you must be patient!
2) Download the WD Diagnostics program and install it. Run the "Quick" Test and then the "Extended" test.
There . . . you are, Bro.
You can use a NAS drive as a storage drive in a workstation, or as a media drive for workstation or HTPC. I wouldn't use them for a boot disk. And you could wring your hands about the "5,400 RPM," but for me, it doesn't matter. I've been all over various threads about my ongoing "experiment," and the basis of the experiment means I shouldn't care much as long as an HDD performs in the expected range -- maybe 140 MB/s sequential throughput and acceptable write speed.
I'm now using 2.5" "laptop" SATA spinners in my systems -- 2TB drives, 5,400 RPM. Those things are stellar so far as they've been put to use in household desktop systems . . .
But I still cannot find a 4-propeller "copter" drone that can lift my computer. YEt -- it IS lighter than with a pile of 3.5" spinners.