I've been using it for personal projects and it's been quite fun !
The comments about Postgres and database XX vs ArangoDB are always the same, this is a choice depending on the use-case, if you have a vague scenario, ArangoDB has good performance on a wide array of use cases.
On a personal note, the main downside is not having any ORM for Golang for example, Node.js doesn't have any worth considering too.
Python seems to have arango-orm, which makes it simpler for small projects to integrate it.
Another improvement could be the graph visualization, simplifying the setup to use another solution would be nice.