不知道是否有哪位有開發者帳號的前輩們試試看，分享給大家心得
這應該會是GM版的前一版吧？
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網路上看到的更新內容：
來源：appadvise
Performance Improvements
As we’re getting closer to the final release, you clearly feel that a lot of improvements were made to make the system faster and the animations smoother. Emails send right away, multitasking animations don’t stutter, and apps are snappier than ever.
AirPlay for music is also performing much better without a doubt.
Bug Fixes
In this beta, Apple has resolved a lot of old bugs. You can now again add your MobileMe account without the system crashing, as well as use the Find My iPad feature.
New SMS Ringtones
We’re hearing (via Macstories) that there are some new SMS ringtones to chose from in iOS 4.2 beta 3 for iPhone.
No more AirPlay everywhere
The default AirPlay button that was showing up everywhere in the past betas (in the default playback control panel), which we were so excited about is now gone. This is very bad news. It’s still there in the iPod app and Safari, but not anymore in the video app, or in the youtube app for example. It makes us think Apple is rather going to go on a per-app basis where developers need to activate it, not to spook away Netflix and the such.
More Control over sounds
You can now handpick which system sounds you’d like to hear or not.
New Google Maps Mode
You can now switch Google Maps to “terrain mode” to enjoy a more traditional view of cartography:
Always Show Bookmarks Bar in Safari
On the iPad, you can now have Safari keep the bookmark and address bar at the top of the screen at all times if you wish so.
