There's a BRS video where they claim that it's sufficiently accurate for hobby purposes.
The software is stunningly bad, but you can get it to work. Wish another company copied the hardware and put a semi-competent software developer on the project. Then it would be a great product.
Despite its problems, it's worth it. With LEDs PAR can vary drastically in areas that appear almost the same to the human eye. I originally bought mine to tune my lights, but have discovered that having PH and ammonia monitored for me 24/7 without worrying about calibration is great. Wish I had bought one from the very beginning, it would have saved me a ton of time on testing.