I think that the Shuffle Play button was removed from some views over the course of some of the recent betas. But it was added back (you should see it in 1.1.1.410) in most views. It just doesn't show up in views that would result in duplicate tracks playing because a track belongs to one or more attributes. e.g. it doesn't show up in the root Playlists or Genre's view because if a track belongs to multiple playlists or multiple genres, it's unclear whether the track should be shuffled once or more than once.

-Rusty

So the 'shuffle play button' is the button that looks like fastforward

I see the Shuffle Play button when I select a Genre on the latest beta.

There was before a shuffle button at Genre level, that allows to play randomly traks comming form all genres. That is not possible now, and it will be nice to have back that functionality.