It's easy to use, it doesn't make any mistakes when you're writing emails with this programmator tool.
I think that its interface is very simple even if there are more features than those necessary from basic email campaigns management needs like scheduling senders lists or autoresponders rules definition etc.. As far as i know we can only create automated workflows via API calls which limits some advanced options such us sending an html version instead text-only ones (or other languages versions) but nothing really annoying so in general everything works perfect! Nothing specific at all just try once :D.