This is a straight forward tool with a familiar admin interface that will make it intuitive for most to use. As a (current) freebie for the pro plan this will do what you need and that is a great deal. If you are a hard core coder you may just prefer plain text style changelogs but I like to brand everything and that is a cool feature here. You can add your logo/header/footer and customize fonts. Even a custom domain is included. At the team level you can do 10 changelogs and manage team as well as remove the powered by. Otherwise you have a full branding here at either level. There is also the option to add js/css so you could really stylize and get creative here.
For really jacking up the branding/styling, I might suggest templates for styling or maybe some sort of styling options for output e.g. how much padding to use between items. This could be achieved with the custom css but it would be more convenient for most I think, in an editor panel or some sort of template options. Perhaps optional paid templates for some additional mrr for the developer.
And an option to output a plain text (changelog.txt or .md) version for download could be useful for some.