Having spent the morning using the app, I'm extremely impressed by it. It's not completely stable - tapping on a character name, for example, occasionally makes the app crash - but the core functionality of reading/hearing/watching the play is rock solid; it's just the auxiliary functions that seem a bit flaky.
The interface switches between portrait and landscape orientations, with different functionality, which is nice. In portrait mode, you see a video presentation of the actor speaking the lines in the top third of the screen, while the bottom two thirds show the printed text, which scrolls to stay in sync with the actors (or vice versa - you can scroll the text and double-tap on a line to sync the video with that line). Difficult words and phrases are underlined, and show a pop-up definition when you tap them (these are the notes at the bottom of the page in the printed Arden edition).
Turn the iPad to landscape orientation and the interface changes. The video disappears (but you can still play the sound if you wish), and the whole screen now shows the text. At the end of each line are icons which take you to notes, textual variations, and small pictures which take you to stills from various performances of that point in the play, explanations of related matters, and so on. Eg, in the storm at the start of the play there's a picture of a ship which, if you tap it, tells you the story of a ship called the "Sea Ventures" carrying colonists to Virginia which was wrecked on the coast of Bermuda in 1609, and whose story is widely considered to be Shakespeare's inspiration for "The Tempest".
Tapping an icon at the bottom of the screen takes you to a screen which shows you where each character is at that point in the play (very useful!), while tapping on a character name takes you to a summary of that character, from which screen you can see all the lines spoken by the character, and jump to the appropriate point in the play from any one.
The home screen also has an item which lets you read all the introduction, essays, etc, from the Arden book, and has a list of supplemental videos about all sorts of related themes.
All in all, a way of thoroughly exploring every aspect of the play. Perfect both for simply watching it, or gaining a detailed scholarly insight into every aspect of it. I look forward to the other plays being released!
One thing to note is that the app has about 2GB of videos which you download from within the app after installing it. That's about 1.6GB of video for the play itself, and another 400MB of supplemental stuff. You can delete and re-download any of the videos at any time (for the play itself they're split up by scene), but it's best to have them all. A good reason to own a 128GB iPad
.