Tried their product on a Magento 1.8 shop. Couldn't try Shopify, as the plugin is not out yet. The integration took and hour and a half, which is nice. The website user experience could be better (couldn't browse all the section of the web page until the integration), but they are working on it. Nice email templates, a lot of triggers to play with. Once configured, it is completely automated. You can use their own ESP, but there is a possibility to integrate with any other ESP, I stayed with Madrill. The price depends on how much revenue they brought you, which is also nice (it is free until you make your first $).
Definitely worth trying.
Easy of use. Email marketing automation.
Some popular CMS not available. No CRM integration yet.