It's very easy to use with no configuration needed at all! The support team are also really good as well - always willing help out when you need it (and respond quickly!).
I don't have any dislikes of this software other than perhaps how long some features take longer then others but they're working hard towards improving these issues by adding new functions etc which helps us understand what we can improve in future versions too :) We've been using premailserver since version 1 so there isn’t much else i would like improved either way :P.