This is really big news, as previously it has been a real case of detective work to confirm that Google have applied a manual penalty to your site, and it obviously can have an enormous effect on businesses.

This is a great move towards transparency from Google, and is very welcome. My only concern is that the language does not confirm that all manual penalties are reported here; it may be that it is just a subset. I'd like Google to clarify that, but otherwise this is a great step.