For a home server what's the benefit you're paying for though? I don't need max performance (I use RAID for redundancy rather than anything else), and a little downtime when I replace a disk isn't an issue.

If you have several drives in the same bay, you're going to get vibrations that severely reduce lifetime of the harddrive. NAS Drives also have much better electronics/mechanics to help them not crash all your data while in use. They won't try to heroically save that one sector and report to your RAID controller instead, meaning you get a much better overview of harddrive defects and lastly

Lastly, NAS Drives have a much lower error rate than Desktop drives due to the usage of higher quality heads that increase error resistance and lifetime.

You want NAS drives for TLER and vibration tolerance.