I mean, with Mailgun you can have inbound email addresses on your domain forwarded to a Gmail inbox, for example, and Gmail also allows you to send email on behalf of those imported email addresses.
We were also doing similar combinations for our startup projects via Google Apps and Mandrill, but it was getting very messy. I just wanted a new domain / new email address, fast. Nothing else. Somehow I would end up with multiple Google accounts, and then Google cut of the free accounts... Interestingly, Mandrill announced the same thing today. I'd rather give up two cups of coffee a month and not waste brainwaves and worries on this admin.
Migadu is meant to get email admin out of people's way so they can focus on more important stuff.