More than simply a Departmental blog, Govspace, as discussed on Twitter by John Sheridan, is a blogging - and eventually a wiki - platform available for other Departments to use,
@purserj We want it to be able to host either blogs or wikis and be easily recognisable - like data.gov.au #gov2auI see this as a similar service to GovDex, which is used broadly throughout the public sector for engagement and collaboration purposes.
The Govspace platform is powered by Wordpress, which I believe to be one of the most powerful, widely used and well supported blogging platforms available on the market. There are tens of thousands of 'skins' to change the design (plus you can customise your own), plus there are thousands of plug-ins adding different kinds of functionality to the Wordpress service (you'd have to confirm with AGIMO which are supported).
So if you are looking to start a blog for your agency and your internal systems don't entirely (or on a timely basis) support what is needed, Govspace is now a viable option.