We use Litmus mainly to get the rich email analytics tracking and to test that each of our communications looks perfect in every platform. We love the tracking code it has as it is far superior to what we get through Salesforce normally. We send our emails through the Marketing cloud due to better integration with Salesforce but we build them, test them, and track them with Litmus. Also, Litmus' newsletter and resources are of great help to keep our communications updated and up to date with the latest trends.
Pros
Great tracking and analytics
Superior ISP rendering testing
Great email builder
Cons
Better CRM integration with SalesForce
Better reminders to make you save your work
Likelihood to Recommend
I've used other email builders in the past and so far Litmus is superior. The ease of use, the tracking, and render testing for different providers Litmus uses are on another level.