I have had one of those 8TB drives in my MythTV box for the past couple of months. Too new to know about long-term reliability, but thus far it has been fast(!) and invisible (no issues).

It sits there long with three 4TB WD Green drives in a mhddfs array. Being the newest/largest drive, it attracts most of the I/O, and has been getting a pretty good workout.

Cheers