For one, Instagram decreased the app size in half which should increase the overall responsiveness of the app. You should also notice your profile screen load twice as faster than before.
Instagram also rearranged a couple of buttons on the app for easier navigation. Those with small phones and feature devices will be happy to find that visuals are simplified to maximize screen space, while bigger devices should now have easier to reach buttons.
Instagram promises its users that, “It’s the same Instagram for Android you know and love—faster, cleaner and easier to use than ever.”