It's comparatively quick and easy to configure as compared to other solutions. For example, Mailchimp is a popular competitor. I find it quite easy comparatively, with less configuration is required. You just need to get the key that's embedded in your code, and you are good to go. Other than that, in one of my projects, I use it to import the pre-configured templates and stuff like that. That was pretty easy, and the simplicity was beyond my expectations. We don't use it, particularly in development. However, we had a good experience. The UI is fine. It is easy to set up. I find the solution to be stable.