pinch-to-zoom is not enabled by default with this update; and, the way to turn on the feature is not exactly intuitive. To enable pinch-to-zoom, you'll need to go into the Settings of your Gmail app, and make sure the option for "Auto-fit messages" is checked. Once that is done you will be able to use pinch-to-zoom.Another odd thing to note is that
The update also adds swipe gestures for archiving and deleting messages. Again, this option can be a bit confusing. The default action will archive messages that are swiped from the Inbox, Priority Inbox, and other regular labels that you've created, and it will delete messages swiped from "System labels such as All mail or Sent". This can be changed so that swiping will delete the message wherever you are.
The last of the "wow, that wasn't there before?" features added is the option to now attach photos and videos from inside the Gmail app rather than sharing from another app. We were all surprised that this was a feature Apple didn't add to its Mail app until iOS 6, and Google is just now getting to it as well.
All of these updates, plus larger previews for photo attachments are available to users running Android 4.0 or higher. So, as of the newest numbers, just out today, Android 4.0 and higher makes up a respectable 34.2% of the ecosystem.
Android 2.2 and up also gets a new Labels API for 3rd-party app developers.
Just check your Play Store for the update.