Having used around 10 email broadcast systems, Maxemail is the best system I have used. The engagement modules allow me to create personalised email for my audience based on how they interact, not simply their profile information. The dynamic nature allows people to automatically receive different emails depending on how they interact across a period of time. Additionally, I am able to store non-user data within the system and merge it in to any email I feel is appropriate for that user. This means we can create thousands of variations of emails with minimal email coding. Add this to the easy-to-use interface and it all combines to create a really good system.
Not a lot. I don't like how some features auto-save and others don't. I would like to see a few new features added - such as the ability to export your segmented list of users BEFORE you send an email. I also think the system would benefit from a custom reporting suite. The data export/insight tools allow you to look at reporting in the system but most marketing departments have their own spreadsheets to maintain. It would be great if a user could say: I wan't the opens, clicks and unsubs from these emails within the past week and for that file to be automatically generated and emailed/ftp'd each week.
Rather than a 'load & blast' mentality, we're able to be far more intelligent with our emails to make sure our email are relevant and improve our engagement stats. We're able to identify wasted emails and then either not send them or send something different.