Scott Main the lead tech writer for developer.android.com wrote in a blog post today via Tim Bray, that with the release of Android 3.0 Honeycomb on tablets, Android started to make a transition away from the menu button and to the action bar. Now, Google is encouraging developers to stop using the menu button and gravitate towards the action bar.
The menu button was customizable in any app to give the end user options that the developer selected. For instance when you hit the menu button on thedroidguy app you get options for news, reviews, about, contact and listen. If you pick another app like the official Weather Channel Weather app you get choices for my location, search and exit.
Main writes Not only should your apps stop relying on the hardware Menu button, but you should stop thinking about your activities using a “menu button” at all.
To that end Main suggests that an apps activities should provide buttons for the important user actions in the action bar. Actions that can’t fit in the action bar go into the action overflow menu (which kind of looks like a menu button).
What does this mean for Android users? Well all it really means is when you get a device running Android 3.0 or higher you’re going to lose the native menu button and have the action bar. Your apps will use the action bar in place of the traditional menu button. This won’t be an extremely hard concept to grasp because on devices that are native to Android 3.0 Honeycomb or Android 4.0 Ice Cream Sandwich, the menu button is gone.
source: Android Developers Blog