I have tried SEVERAL. I still use SendGrid for certain things. As good as they are at triggered sends and transactional mailing, they are far from the most user-friendly in terms of email marketing. I've dabbled in MadMimi, Constant Contact, and everything in between. The hardcore corporate pro's seem to like Klaviyo but I think it's overkill. I always come crawling back to MailChimp. Save yourself the future headaches and just go with MailChimp!