If you have cracked or rooted your Android device, Miitomo will kill it dead. This is not a bug; rather, this is a "feature" courtesy of Nintendo's Neolithic attitude to phones and non-proprietary technology. Be very, very careful.

It's a pretty fun time-sink if you're just waiting a few minutes for something like, say, a kettle to boil when making a cup of tea, or the bus.

The question asking and reading other answers is probably only half of the game, I'd say. There's also a focus on dressing up your Mii. You get money from things like answering questions, commenting on other people's answers and daily bonuses, and can buy clothes to dress up your Mii. You can also make "Miifotos" where you can pose Miis and add effects to make funny responses, which can be sent as replies to answers, shared with friends or just saved to your phone.

Here's a Miifoto I made. Here's another, showing my skill at making masterpieces. Some of the options are amazing

It's not perfect though - there's a few issues with I assume memory load where the app will close itself sometimes, and if you swap apps, it will restart itself (losing what your were doing before) but as a time waster it's pretty darn fun.