Pros
Mailchimp is very easy to use and has plugins for 99% of the other services my company uses online like our web host, G Suit, forms system, etc which is awesome and works amazingly. Their API is super smooth and simple so it is easy to import and sync all kinds of customer data from one service to another. The analytics mailchimp provides from campaigns is also super helpful, and so are their new automated tasks sending out automatic emails to customers after purchase or after abandoned carts.
Cons
My two major complaints are the price points and the flagging system. If you have a very small company the prices are pretty great, but as our customer database grew the prices jumped severally. I wish there is a way to pay less by opting out of some of the features we don't need or use, but it's a set strict pricing tier, all or nothing. Even with the higher prices my company kept on happily using MailChimp, until our account got flagged for 3 false reports. From the research, we investigated it appears that a rival company had their employees sign up for our mailing list, probably for market research keeping an eye on our sales which make sense, until those accounts reported one of our newsletters as spam causing MailChimp to immediately suspend our account. After MONTHS of being a paying customer with no issues, I feel them instantly suspending our account without first contacting us is unacceptable. The automated hoops they made as jump through we ridiculous, and the response time, once we jumped through those hoops, took DAYS - Days we had to pay for even though our account was suspended. two weeks down the road we got our account reactivated, but our request to talk to a member of their team was ignored. Mailchimp treated us guilty until proven innocent, which I would get if we didn't already have an impeccable record with them. We had over a year of 100% upstanding email campaigns using their service and feel like we were treated VERY unfairly. What happens next time that same competitor false flags us, forcing us to pay for service time we can not use? Because of that, I am actively researching other service providers, specifically ones that have actual human employees that reach out before drastic measures such as suspension.