I love all of this software, it makes my life easier when sending out mass amounts or even just one message at time! It's also great for tracking your campaigns as well because you can see what was clicked where which leads me nicely into other reviews here about how easy that interface goes hand-in-hand so easily!! Nothing really comes up but maybe some people have had issues using them? Other than those two things nothing bad came from us trying pilotsend over several years now.
We do not use any third party services like MailChimp etcetera anymore instead we rely solely upon our own tools (Pilot Send) along side Google Forms/Forms API integration via Zapier if needed by clients who are interested in getting more data points around engagement rates.