I like that you can create campaigns really easily, as well as add new segments to your lists/subscriber files or senders too! The interface is fairly intuitive if it's something you're familiar with from other platforms but there aren't many extra features beyond what we need for our needs so far which are quite basic, nothing special here yet at least!! You have to be pretty organized about how things go into each list before sending them out though - otherwise they could get buried somewhere between folders or emails sent etc.
It would help having more automation options such as being able to schedule an email once someone has already been added to one of my mailings rather than creating duplicates and adding people manually every time. Having easy access to all contacts within CRM without needing separate tools helps save me loads of man hours over using multiple systems which take forever just because I'm looking through different tabs & screens trying to find who belongs where.