Really helpful, as long as they're done well and respect the candidate as much as possible.

In my experience, they provide a great way of understanding a candidate's skills. It also lets them work in a low-pressure environment with their own tools, which tends to let people achieve their best.

I actually recently launched a service to help make managing take home tests through git more efficient: https://candidatecode.com

It's still early stage, so any feedback is appreciated