This app works well, though there are a few shortcomings:
1 - They should really integrate with Bing Merchant Feeds as well. It would be really simple as Bing accepts Google Merchant Feeds, but the app only works with Google's API, and there's no way to export the data and upload it to Bing.
2 - There's no way to bulk update custom labels, which would be really useful. You can do this via the new bulk edit products feature in Shopify, but it should really be possible in this app.
3. If your description for your product is too long, the site will error out and not upload your reviews :(.
But it works, and we uploaded 300+ cell phone boosters and signal enhancers after spending a few hours fixing all the custom data necessary.