Absolutely love this app!
I installed it on two client Shopify sites last year and the results are extremely impressive. On one, the shop owner no longer does his own advertising as Order Legend brings in enough sales for him and he only pays a commission on those sales with no up front costs. On that particular shop with the products sold, the cost per click can be quite high (for that industry) as there is a lot of competition but the owner sleeps well at night not having to worry about managing a PPC campaign or trying to hit a specific return on ad spend to be profitable.
The other shop has a decent daily advertising budget (but never quite enough) and as soon as the budget is depleted, Order Legend kicks in and starts displaying the ads instead and of course, no sales = no costs for the client!
Both sites upload reviews to Google Merchant Centre and I particularly like the way those star ratings also show on the ads that Order Legend is running when the clients own ads are not.
Everyone with a Shopify store and a Google Merchant Centre account should be using this app to generate more sales. It's literally risk-free :)
