Google launched a new app last week that augments Gmail on mobile devices with reminders, assist, tasks, flight information, attached photos and more. Inbox isn't a replacement for Gmail -- not yet, anyway. It only works with Gmail accounts and is intended as an add-on feature to highlight the incoming mail that each user deems important. Google assumes what's important, and each user can tell the platform what they want to see and how often they want to see it. Here are a few benefits and challenges.