Well I took EmpowerGMAT first since I was thinking about going the MBA route before I decided to focus more on public service my scores went from 510 to 680 after about 7 weeks of studying, and I'm having a similar experience so far with EmpowerGRE. From the the first PowerPrep to my most recent Manhattan GRE test I've gone from a 152 to 160 on verbal. On math I've gone from 149 to 161, and there's still a lot more training left in the plan. That's why I wanted to chime in here when you asked. I have 2 experiences with Empower, and they're batting 100%. That, and the Magoosh vocab app is just working for me.
Keep your head up Arm. Crack the tactics, and you'll break through.