Update: The system is all installed now, and the batteries work great, hence I can update the rating to 5.
As a crude test, I ran the 750 Watt microwave in 5 minute bursts, and after 45 minutes the battery was still holding up and I was getting bored with the test, so I stopped.
I am very happy with the batteries. I haven't capacity tested this yet, still busy installing the system and some parts are still outstanding. However, delivery was very quick and I was very gratified to receive a call from the supplier (in China) to check on my satisfaction. I will upgrade this review once I have capacity tested the batteries.