Just downloaded and installed Boxee on my mini (see below). Then downloaded and installed the Justin.tv app.
On load, the app apparently does log me in to Justin.tv. However, the app then immediately presents an error screen:
[ OK ]
On 'OK,' a 'not found' message is revealed:
"Sorry, we didn't find any live channels in the selected subcategory / language. Please try expanding your search."
The menu choice in the upper left is titled 'Favorites.' The menu choice on the upper right is set to 'All Languages.'
The error message occurs whether or not there are live broadcasters in my set of followed channels at Justin.tv.
In the web-based Justin.tv UI, there is no 'Favorites,' although one may 'Follow' and 'Unfollow' a channel. Therefore it is my assumption that 'Favorites' represents the same data set as 'Followed' channels.
If a Followed broadcaster is providing a stream, I can see it by browsing to it under the appropriate category.
I do not see a way to 'Add to Favorites' while watching a selected stream.
mac mini 2ghz Intel Core Duo, 1gb, osx 10.5.8 / boxee 9.23.15885