Specifically, I think anything done with NotificationCompat can be done using the default API (level 8). What am I missing here? What does NotificationCompat introduce that cannot be done using 2.2 API?
Source: http://developer.android.com/sdk/compatibility-library.html#Notes
You can use things like NotificationCompat.Builder#setLargeIcon(Bitmap) to allow you to take full advantage of Android 3.0+ with things like the large icon, while maintaining compatibility on versions of Android prior to 3.0 that do not support such things.
Though its old question, now NotificationCompat can also be used to create wearable specific notifications. More information on this google's developer guide.
http://developer.android.com/training/wearables/notifications/creating.html
It allows you to use the NotificationCompat.Builder class, a compatibly version of Notification.Builder from API 11+. As its name suggests its an implementation of the builder pattern, which seems to be its main advantage over the pre Android 3.0 notifications.
来源：https://stackoverflow.com/questions/10071086/why-is-notificationcompat-needed