In the guidelines found in http://developer.android.com/guide/practices/ui_guidelines/index.html for menu and status icons, we have distinctive design approach for Android 2.2 and earlier and Android 2.3 and later. My app is going to support Android 2.2 and later. I was thinking that i should follow the 2.3 and later guidelines. Do you agree?
You can follow multiple styles by creating subfolders with the correct android version specifiers inside your res/ folder (e.g. drawable-v11 for API 11 - check the official documentation here). So I suggest supporting multiple styles.
This is obviously a bit more work. To make this easy for standard icons like notifications, check out the Android Asset Studio. This is a small webapp that creates these icons to your specifications and builds a zip with the multiple styles, already sorted into the different res/ subfolders.