First, before you select the upgrade, go to apps>help center>before you Upgrade to Android 4.0 and watch the video. Also from the help center app touch the "tips" tab and read up on what is new on android 4.0. How to find the old items from Gingerbread that you have come to enjoy.
Screen shots can now be down by holding the power key and volume down button.
The favorites tray at the bottom now holds five apps
There are numerous changes and you may be put off by them at first but may really like it. Here are just a few changes you will notice right off:
Lock screen access is different but can be modified.
Notification bar is dark now which is better for your battery. You can swipe the notifications left and right to delete them or just hit the X at the top to delete them
There is face unlock now but this is not proven to be very secure
You can create folders easily by dragging like apps and dropping them to a similar app. Say you have facebook, yahoo messenger, twitter and other social apps on one of you home screens, touch and hold one of them and drag and drop into another one. Once you have added all you social apps together, name the folder to clean up icons on your home pages.
Widgets are now located in the app section of the software instead of long pressing the home screen
The software now recognizes printers easily and are easily set up
Camera editing software has been added and it quite cool.
You should be able to take snapshots during video operation
Contacts are now a people app and the format has changed as well.
Settings menu is changed somewhat also
Overall I find the update to be great. The issue I think many will have is that you may have multiple application downloaded that may or may not work well with Ice Cream sandwich so if you find that the phones starts bugging out for whatever reason, then you may consider doing a factory reset. I wouldn't do this right away. If you just do the update, you should not lose your contacts, photos or music or files that are saved to your sd card.
Google voice enhances vocals commands
Swype keyboard still available with improved input
It may be best to perform the download while on Wifi (especially if you are not in an area where 4G is strong) I did my on 4g and have had no issues. Ultimately the experience is much better. Some have experienced issues with battery life or actions but not all of us. If you need help with creating a function, just post on here or do a search for the action on the forums and I bet someone has covered the topic.
Most of all, good luck and have a little fun, but do expect the format to be completely different. Give a week or so to play with what new menu screens are available before judging your battery. You will spend quite a bit of time trying the new functions so the premature battery calculations may not be true to normal use once you establish your personalization
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