I'm pleased with the Venom Pro Duo I just bought. I'm even more pleased with Venom's customer service. The first one I bought had a bad LCD backlight. Everything else worked, but it was hard to see the screen. I sent them a message asking if it was just turned off somewhere, or defective.
They had me send them a short video showing the non-lighted screen, and after I did that they immediately sent a replacement out and told me to just toss the defective one. The replacement got here in less than 2 business days.
I don't see much of that kind of customer service anymore - it was a really nice surprise, and I'll definitely go back to them the next time I need something they make.
As to batteries, if I'm not mistaken if you crash due to a system fault while using a non-OEM battery, Yuneec will deny your warranty claim, so because of that I will only use original Yuneec batteries through the end of the warranty.