Video files in particular, do not play.
For video files, a thumbnail is shown but tapping it does nothing. See [[Blowing a raspberry]].
For audio files, with mp3 support most embedded audio files now play, more could be done to improve the UX, but basic audio playback works. Additionally prononciation guides or other audio links embedded in templates still do not play. See linked task/discussion in comments below.
The gray box also has too much padding, so that it covers some of the surrounding text/article content. See for example [[When Johnny Comes Marching Home]].