Doesn't matter whether it's good or bad, I already have an existing Maven project I would like to try this in. Besides, Maven and Gradle are simply what I'm used to when working with Java projects. Yet another build system is about the last thing I need. I consider building Java to be a fully solved problem.

I use it in a few projects, all are polyglot monorepos. I think bazel really shines in that setting. I have one tool to interact with my codebase. I use it to manage all build, test, and deploy, but also code generation, running local dev servers. I think its worth the hassle of setting it up for large multi language projects.

As far as I know it’s not necessarily bad, it’s just not standard, especially not for java projects, so it may require strange file hierarchies.

Bazel doesn't enforce a structure. Bazel makes you add WORKSPACE and BUILD files throughout your project to describe your targets and their dependencies.