• "Connect to iTunes" still exist at the first setup. Even the MobileMe still exist in this pre-iCloud era.
• 'iPod' is gone. Now changed to Music app & Videos app.
• Green bubble chat: SMS. Blue bubble chat: iMessage.
• Yay! Free rotation editing in Photos.app.
• After created an iCloud account in the iPhone, it appears in Notes.app. And also in Contacts: All iCloud.
• Double click the home button for the camera icon in the lock screen.
• You can tweet your photo from Photos app without Twitter app installed. Though there's no sending-progress indicator so you won't know if it sent or failed.
• Notification Center doesn't interupt Nike+ GPS in indoor mode.
• iMessage cannot send video file. :-/
• Unprecission keypad. Tap "T" but typed "R" or "Y" instead.
• Video library is not accessible for other app, incl. Tumblr. (pic)
• Twitter, iMovie etc can access the video library but cannot process the file. (pic) If you want to share video, you can upload it from Photos.app > Share > Email. I can upload video file via email to twitvid. http://www.twitvid.com/CWZMP
• Ergonomically, using volume button as camera button is not convenient. The other fingers keep blocking the lens.
• BlogPress fails to upload blog.
• iBooks is buggy.
• Photo Stream synced after more than 10 minutes. And not all the photos are streamed.
• Problem with email sharing from Photos.app. Takes forever to send for a 200kb photo.
• There's no Weather & Stock in Notifications setting.
• Home Sharing's podcast tab is missing in Videos.app. But I can watch video podcast shared from Home Sharing in Music.app, not in Videos.app.
• The Notification Center UI is too tiny for iPad. Waiting for the 'HD' interface.
Overall: there's no turning back to iOS 4! :)