The overall rating reflects the current state of the app. It accounts for all app reviews but prioritizes the most recent ones.
I can see how the app would be wildly valuable if you can get it to work for you but Dave's less than stellar customer service is really a turn off. Don't dare send him an email asking a question or having a problem because he is very defensive and will reply quite rudely. If you don't do everything EXACTLY and if - god forbid - you don't understand something, you should know this is "Hence why [he] wrote a nice 30 page manual for it." Note to new users - the trial doesn't automatically transition to a subscription unlike every other back-end app after the free trial period. Just take note of this because if you spent a lot of time using the app to start the store but then you don't go back in to start the app, you will lose your work or have to do a portion of it again.