We switched to MailGun after this Mandrill change and it's a pretty nice setup. The one thing that is a little different about it (at least in comparison with Mandrill) is that you have to set up a bunch of DNS changes and then wait for those to take effect -- so it's not something that you set up in an afternoon. That said, they track the DNS changes and follow up a couple days later when everything is ready to go, which still makes it a pretty smooth setup.

It's just not something you can rely on if you need your transactional emails set up *today*.