What does the company do well? Their support and account management is accessible and typically quick. They also alerted us to issues in our account so we can rectify them before they became too costly.
What does the company not do well? Preview emails, and the web interface is a little slower than other services we've used in the past. Their reporting is a little confusing, that experiments and regular campaigns are separate.
What do you wish you had known about the company before using? Pricing went up dramatically when we went over our email quota.