I have the first generation and it's installed in a Kiss
It's plenty loud for me, you have plenty of options to set up the type of alarm sound and length. The software works flawlessly and customer is the best I've ever seen and you can't beat the price of that unit. Battery life is plenty long.
When going up the alarms can be deactivated and you get only 1 beep at around 100ft. The alarms will all sound when coming down. There's no detection of fall speed to mute freefall alarms like other manufacturer but honestly I kind of like it. It reminds me of my hard deck on every jump.
With the Kiss, I need to remove a screw to get it out of the helmet because the adapter mount doesn't allow the USB cable to enter the connector from inside. I find this part annoying but I don't change my alarms all the time. According to Aon2, Gen 2 will eliminate the need for the custom adapter mount for the Kiss but I don't know if that issue will still exist. I also have a X2 and they put bluetooth on that one so maybe in the future it will be implemented.
All in all, I'm very satisfied with that product