Mostly for games. Occasionally for viewing txt files (it's a brilliant option when you need to take something with you but don't own a printer), viewing images (reference photos for drawing away from a PC) and digital drawing.
I don't watch videos on it; I tried it once but given how long it took to convert the file it doesn't really seem worth it. But I don't use mobile video at all, so admittedly I'm not the intended userbase for that. No music either, MP3 players are smaller and the sound quality's a lot better.