The app has gotten a complete overhaul of the UI, adding the tabbar at the bottom to make it easier to navigate and find interesting content. The Explore feature has been refreshed with swipe gestures to navigate between photos. But, one of the best new options is that the app allows you to choose from any of the camera apps installed on your device to take a picture, so you can stick with the stock camera, or get fancy with an HDR app, or get faux-fancy with Instagram.
Advanced users haven't been left out either. The search function now shows HTML content in comments and descriptions, so you can easily link and add information. And, the app can also now edit metadata on images, which is a big one for pro users.
If you want to try out the new Flickr app, it's available for free in the Google Play Store.