It's great for side projects without the limitations of Heroku's free tier. Lots of plugins (Postgres S3 backups, Lets Encrypt certificates) are icing on the cake.
I work on a selection of internal applications and services and we run everything with Dokku. I was skeptical at first because it made initial [legacy code] deployments a bit of a pain, but I’ve been converted. Not sure I’d run everything that way but for small-scale applications it’s a breeze. And because you have to do the sysadmin work yourself it’s a bit more flexible than Heroku.
[0]: I know this is not best practice, but this is a small project and this is a hack that I fully know the tradeoffs for.
Hardly seems like Heroku is in the wrong there