Android 3.1 Feature

The Android 3.1 platform adds a variety of refinements to make the user interface more intuitive and more efficient to use. Android 3.1 is an incremental platform release that refines many of the features introduced in Android 3.0. It builds on the same tablet-optimized UI and features offered in Android 3.0 and adds several new capabilities for users and developers.

Android 3.1 Performance optimizations

Android 3.1 includes a variety of performance optimizations that help make applications faster and more responsive. Some of the optimizations include:

A new LRU cache class lets applications benefit from efficient caching. Applications can use the class to reduce the time spent computing or downloading data from the network, while maintaining a sensible memory footprint for the cached data.
The UI framework now supports partial invalidates in hardware-accelerated Views, which makes drawing operations in those Views more efficient.
A new graphics method, setHasAlpha(), allows apps to hint that a given bitmap is opaque. This provides an extra performance boost for some types of blits and is especially useful for applications that use ARGB_8888 bitmaps.

Android 3.1 UI refinements

UI transitions are improved throughout the system and across the standard apps. The Launcher animation is optimized for faster, smoother transition to and from the Apps list. Adjustments in color, positioning, and text make UI elements easier to see, understand, and use. Accessibility is improved with consistent audible feedback throughout the UI and a new setting to let users customize the touch-hold interval to meet their needs.

Navigation to and from the five home screens is now easier — touching the Home button in the system bar now takes you to the home screen most recently used. Settings offers an improved view of internal storage, showing the storage used by a larger set of file types.


Source:
http://developer.android.com/sdk/android-3.1-highlights.html