Still working fine as of last night. Our affliction locks are getting an average of 50k dps out of the voidlord across all attempts. It does seem to be benefiting from affliction mastery (our destro lock went back to GoSac after poor results with his voidlord). No positioning required, just regular follow/assist. We did macro voidlord to MG and FF since he doesn't maintain perfect uptime.
We have ~20k mastery raid buffed. Your mileage may vary.