I like that you can use this app to send text messages, calls etc without having your phone with you or even using wifi at all times! It's great for people who want more freedom when it comes down to mobile devices especially if they're travelling often but also just as an alternative way to communicate while away from home/office sometimes too (e.g., during long train journeys).
The only con would be battery life - although not really much because there are several different ways to conserve…