Thanks @loren, I have updated this comparison table accordingly.
MailChimp has a new SMTP service with a free plan now, called Mandrill (mandrill.com), and the STS product is being phased out. Let's get this comparison up-to-date! I've already added Mandrill and removed STS from the larger comparison at: transactional-emailing-providers-mailjet-sendgrid-critsend
Awesome service! Blows away the incumbents and has mobile monitoring apps! You MUST try it!
SendGrid's service is impeccable.