There are a few things that we think set Mandrill apart from the pack. Our application is designed with responsiveness in mind, and we have mobile application on both of the major platforms so you can get access to your email stats and reputation wherever you are. We have search and analytics deeply ingrained in the application in a way that is fairly unique - letting you see your emails in context and trying to derive the context for you when we can. We also integrate deeply with the main MailChimp product. They use the same underlying delivery engine, the same templating and content personalization systems, and we have a heavy discount for users of both products.
Mandrill's still a rapidly iterating product for us, but we think we can take the same sense of usability and power that we have in MailChimp and extend it to email more broadly.
Not yet. The inbound system right now is really basic - we'll parse out the messages and deliver them to a webhook, but we won't munge it much beyond breaking apart attachments and things.
Yes - the pricing is flat rate. Right now charging for inbound emails is turned off since the feature is so new and basic, but inbound emails will be indexed and tracked the same as outbound emails, so they'll be charged the same.
Mandrill's still a rapidly iterating product for us, but we think we can take the same sense of usability and power that we have in MailChimp and extend it to email more broadly.