The overall rating reflects the current state of the app. It accounts for all app reviews but prioritizes the most recent ones.
The search functionality didn't work. I tried Custom Fields app "the orange" background app on the apps store. It's the app you'll need if you want user friendly. I recommend MetaFields Pro to come out with a better search functionality. The whole point of using this product for us was to import and export products in bulk and edit them in CSV format. How the heck else do you manage 10,000 plus products.