[HTC One X] android_master:
Keyboard

The platform's dictionaries are now more accurate and more relevant.

The language model in Jelly Bean adapts over time, and the keyboard features bigram prediction and correction.

You can now switch languages quickly with the dedicated language selector key on keyboard.

You can use custom keyboard input styles for more than 20 languages, with keymaps for QWERTY, QWERTZ, AZERTY, Dvorak, Colemak, and PC styles.

You can choose the input styles that you want to use for each keyboard, and use a hotkey to switch between them while typing

Messaging and Talk

New notifications display the full text of incoming SMS messages. When receiving an MMS, you can view the full photo in a notification.

When entering recipients for an SMS or MMS, a new UI collects recipients as chips, making it easier to compose messages.

Talk features a new notification style.

Notifications

You can now take action on notifications directly from the redesigned notifications shade.

Notifications from the same application are grouped together, and the first item is automatically expanded. You can also pinch notifications to expand or collapse them.

You now get an image preview in notifications after taking a screenshot. You can quickly share the screenshot directly from the notification.

You can lock automatic display rotation from the notifications shade on 7" tablets.

For Wi-Fi only devices, quickly see the SSID of the access point you're connected to from the notifications shade.

You can now touch-hold a notification to identify the application that created it and turn off notifications from that application if needed, as well as uninstall the application.

Networking

Wi-Fi protected setup is now supported with WPS push button and PIN support.

A new setting lets you stay on mobile data and avoid nearby Wi-Fi networks with poor connections.

News and Weather

News and Weather is updated to improve freshness and power consumption.

People

The People app is more buttery with smoother animations and improved search performance.

The People app now retrieves high res photos automatically for Google contacts with public Google+ profiles and displays higher res photos (720x720) on certain devices.

High res photos set on Google accounts will be backed up and synced across devices.

The People app has a new 7" tablet layout that is optimized for the form factor.

You can now quickly add your favorite contacts to a home screen, directly from the contact's details page.

The People app helps you organize your contacts and reduces duplicates with an Improved auto-joining algorithm.

You can now clear the frequently contacted list from the favorites tab in the People app.

Phone

When you miss a call, a new notification lets you return the call or reply by SMS with a single touch.

Incoming visual voicemails are displayed in a new notification that lets you play the message with a single touch.

When a call is ongoing, a new notification lets you hang up the call with one touch.

As part of Project Butter, the dial pad is more responsive. Call log scrolling is buttery smooth, and swiping between tabs in Phone is quick and fluid.

You can now clear your frequently contacted list in the favorite tab of Phone.

You can now add phone numbers from the call log to existing, read-only contacts.

Settings

Accounts are now displayed in the primary Settings view so you can easily see all the accounts you're signed into on your device.

You can now easily access all Google Privacy Settings in one place by selecting your Google account from Settings.

System

Device encryption is now more reliable, and periodically reminds you to decrypt your device. Now, SMS messages and calls are declined when waiting for decryption.

You can long press the 'Power Off' option in the power menu to boot your device to safe mode.

A new 'Reset app preferences' button lets you quickly reset default applications for specific activities, background data restrictions, notifications suppressions, and more.

A redesigned dialog with larger icons lets you intuitively choose your preferred application for specific activities.

Google Apps Device Policy on your device may now override the 'keep screen awake' option from developer settings.

Text-to-speech

Jelly Bean introduces a new conversational text-to-speech voice in US English, available as both a network engine and an embedded engine via the TTS API.

Voice Typing

A new embedded speech recognizer lets you use Voice Typing even when you don't have an Internet connection.

Widgets

Jelly Bean makes it easier to personalize your home screen. As you place widgets on the screen, everything else automatically moves to make room.

When they're too big, widgets resize on their own. If you choose to resize a widget, apps and widgets will now also move out of the way.

You can now quickly remove apps or widgets from any home screen by picking them up and flinging them to the edge of the screen.

Launching apps and returning back home are now faster and smoother.

The new Google experience on Android