Once you have clicked on a Play icon on a picture - or on the Player controls - then you can start, pause or restart the video by using the control buttons immediately below the video screen.
As soon as you tap the input area for the headline, the keyboard comes up from the bottom of the screen and a little keyboard icon comes down to where your profile picture usually is.
The tabs along the top make it very easy to view your friends timeline, mentions, direct messages and even popular topics, and including a picture in your tweet is as simple as selecting the camera icon (you can also view tweeted pictures in the app).