I like that you can create schedules according to your needs. I haven't found any downsides. There is a free version that I would like to try, but I haven't yet. I am solving the problem of sending emails to a number of users. It is very easy to create a schedule that will send out the same email to multiple users. I like that it is easy for me to use as a developer.
It's also great because it runs my crons off Heroku. The only thing i dislike about this tool is how expensive it is compared to