Very good. I like this app but it takes some setting up if you already have loads of products. Could do with a better export function instead of a messy CSV file.
This is a great app that does what it says on the tin - and it provides a feature that Shopify sorely lacks.
However, be aware that it does not take into account discounts, gift cards, shopify payments fees, or anything else; it simply provides sale minus cost of goods. This is really useful for getting a rough idea of your profits but not ideal from an accountancy point of view.
Given the limitations, I don't think that this is a $15 a month app, but if it was $5-7 a month I'd pay for it without hesitation just to save myself my P&L calculation hassle. However, that is not to say it is not a great app and I would certainly recommend it if you need the functionality and can justify the price - easy to get started, easy to use, and gives you what you need.