(should probably note that by 2.5 inch what I really mean is usb bus powered. It's going to sit hidden in a shelf, I really don't care what size it is a long as it doesn't need a separate power cable)
Nah... the WD Reds are optimised for NAS (they are rated for double the load/unload cycles over, say, the WD Greens) but they can be used elsewhere as a regular drive too.
I nearly bought a Toshiba external drive that was on offer in Tesco (seen it without an offer for the same price since though) and was going to rip the HDD out of it. Luckily I'd found out the drive inside has a proprietary connector soldered to the drive. And the USB connection on it is crap and comes loose causing connection problems.