It's wonderful tool and has simplified workflows for many, just be mindful of its one giant security implication. Should your database credentials ever leak in any way (lost/stolen property, incorrect git commit, screencasting mishap, ...), having an Adminer/phpMyAdmin instance running on an otherwise unrestricted address, you're opening up (quite literally) your server to a world of trouble.

(I speak from experience. I've seen a lot of credentials leak together with source code. This meant I saw "secret" paths where Adminer was hosted on a given site. Having database credentials meant I didn't have to somehow circumvent network security to get to the database itself. [Yes, I disclosed all of this to the server operator and even got a measly $50 gift card out of it :-)])