I like all features but most especially being able to send out mass email campaigns without having to go through each individual person's phone number one by one! Also when sending emails with large attachments they will sometimes just disappear or get lost somewhere within my inbox which is very frustrating if not noticed right away as soon as possible so this feature needs improvement greatly!! The only problem we have had was getting our account setup correctly at first (it took 2 attempts before it worked).
Our customer service team has been great though helping us figure everything else out. Great product overall - would highly recommend trying them out! We are using their automated lead generation system called LeadSparks where users sign up via social media platforms such as Facebook & Twitter then receive follow-up calls from sales people who try sell more products/services etc once contacted.