The behavior of the Theater View buttons is directly effected by the last state of the Standard View -- by this I mean that what you had highlighted in the tree when you last left Standard view will change how the buttons in Theater View work.
For example, the Standard View is currently showing the "Audio" tree when I switch to Theater View, select an album, and start playing it. I then navigate to the Theater View "Playing Now" screen. I hit "stop," and when I hit "play" again, the songs currently on screen in the "playing now" list do not start playing. Rather, the first song on the "Audio" list (which I can NOT currently see in Theater View) starts playing. If I go back to Standard View and switch to the "playing now" screen, THEN go back to the Theater View screen, the results are different. In this case, whatever is showing on the Theater View "playing now" screen DOES start playing when I perform the same steps as above.
In other words, the playback behavior in Theater View is directly effected by the way the Standard View was last left before switching to Theater View. It would be MUCH more intuitive if whatever was on screen in Theater View took precedence over the last seen state of the Standard View. As it is now, I have to remember to switch the Standard view to "playing now" before openning the Theater View. Otherwise, the results of hitting "play" are not consistent or intuitive.
I hope that makes sense.
Larry