Well I tried it a few times and it's useless. The only reason they are popular now is because companies figured out that they can hire cheap people this way. If you agree to such a test when you have done a lot of these tests in school, you have public work that is available for inspection and so on, then you are ready to work for cheap. Nothing wrong with that.
It could be a good starting point, but it totally depends on how each of them look at it. Personally, I hate it too.