I've been using Google's contact and calendar syncing increasingly, to the point that they are almost indispensable to me. Most critically, when my last iPhone broke I only had to wait a few seconds for my new one to download all of my information from the cloud. The addition of push email completes Google Sync's basic exchange functionality and establishes it as a robust (and free!) mobile cloud suite.
Update 9/23: Is this killing anyone else's battery life?