It works pretty well out of the box and support was quite fast.
However they do overcharge on usage fees due to their definition of what an order is. If you are a store like us that has a lot of unpaid orders that are cancelled or orders that do not require shipping, you will get charged on all of those too. In my view it doesn't much make sense to charge tracking management for an order that does not require shipping and will never be shipped.
We did raise this with them and they don't want to change their definition as they say it would affect other stores using the app too i.e. they must be overcharging a lot of stores and don't want to lose that revenue.
UPDATE: Their reply below is factually incorrect. They charge for unpaid orders. Very deceptive to admit it privately and pretend it's not happening on the review page. Come on guys, be honest!

Nice app, but extremely frustrating customer support and upgrade experience. CS will tell you that all data during free trial would be wiped out, no proactive suggestion or advice till we chase, they just ask you to say goodbye forever to your all-gone data.

Do not really know if we should continue with this app even though we have already paid for the upgrade. No one is getting back to me and explain clearly where my data has gone. We are having some trust issue with the app.

La aplicación parece buena, pero debería permitir hacer el rastreo sólo con el número de pedido, me parece que se deberían darnos esa opción y dejar nos decidir si pedimos mas datos o solo uno para decirle a nuestros clientes dónde se encuentra su pedido. hacer fácil y simple, pedirle más datos me parece complicarle la vida a ellos.

There's better apps. Needs room for improvement