Android is here, and as to be expected with a Google-made mobile OS, there's a bit of Google App fanciness going on. In fact, it's designed with Google Apps in mind so much that whether or not you're a user of Gmail and other services might determine how useful the phone will be to you.
The G1 will
be the first phone to offer push Gmail, which is something we're expecting to see on the iPhone in the not too distant future. Gmail also features a Google Talk presence on Android, thanks to the fact that Gmail gets its own mail app while all other mail services are relegated to a simpler one. You can sync you contacts and appointments with the G1, but only via Google's services; no Outlook and Exchange support here. In fact, you must have a Google account to use this phone, according to Walt Mossberg.
Google Maps offers street view that you can control using the built-in compass, turning the phone around and looking around like you're actually there. A neat gimmick, but we'll see how useful it actually ends up being.
Here's a video Google released on Google Mobile Apps integration: