Got it too... I was already on the GDR3 preview, but after that app update this a.m. I checked for phone updates and got Black in a single smooth process. FYI, my temporary files are now stuck at 814 MB which will not clear. Oh well...
OS version: 8.0.10521.155
Firmware revision number: 3051.40000.1349.0002
Hardware revision number: 6.0.0.1
Radio software version: 1.0.202158.3
Chip SOC version: 8960
Lumina Black
RM-821_eu_euro1_425