Depends... my NAS is mostly used for video/audio archives and generally only one device in the house using it, playing back a single file, or listing a directory. Would probably be fine in that use case. Beyond that, it's used for backups.

Seems like a decent use case. I'm not sure how well they'd work in a NAS with Raid-5/6 though. I'd been considering a new nas with 4-6 drives at 8-12TB already. Random I/O isn't my primary use, and I'm sure there are others at these sizes.