I like how easy it is for me as an admin, or customer service rep-to use this system! It's very user friendly - no coding required (although you can learn!) You don't need any extra software installed in order to have email deliverability set up within minutes of purchase.
We've been able to send emails from our web site without having multiple accounts at various providers. Also has helped us keep track of who opened each message we sent out so that we know which ones did well vs those that didn't get read/opened by recipients.