The Verge reviewed the Amazon Fire Phone.

Dynamic Perspective is meant to keep the screen simple, showing you only information when you ask for it, but it mostly just hides useful information. Exposing that information then requires such finesse that for a long time you’ll be seeing things rapidly flicker in and out of existence, not knowing how to make them stick around or find them again. Dynamic Perspective makes for awesomely fun lock screens with much more to them than first meets the eye, but it does nothing to meaningfully improve the smartphone experience.

A clever phone:

You’re entirely reliant on gestures and flicks of the phone to access these menus. Most apps have no indicators or helpful icons; you just have to open every app and twist the phone around like a lunatic to find things. You can’t even see the time without tilting your phone just so. An errant buzz is your only indication that you have a notification, prompting you to cock your wrist or swipe down from the top bezel to open the notification windowshade. None of this is explained, none of it is intuitive. Dynamic Perspective makes everything look cleaner, but makes actually using your phone a lot harder. I don’t need my phone to be clever, or spartan. I need it to be obvious. The Fire Phone is anything but.