Those of us who are familiar with smartphones know that one of the toughest things to get right in a user interface is alerts. Alerts are not only what pop up when you get a new message, but also what stays around if you miss the initial alert -- indicators and whatnot. Windows Mobile Pro has an annoying pop-over Windows that grabs your attention. PalmOS has a little tiny Bell icon that appears in the Upper Left. The iPhone has a pop-up window and then nothing except numbers on the home screen.
Android on the G1? It has the "Sliding Info Blind," which is a very subtle line at the top of your screen which displays a preview of your incoming message. You can tap it to open the message or, you know, ignore it and continue what you're currently doing without having to hit "cancel" or "close" or "ignore" like you do on many other platforms.
We're starting to get overwhelmed with all the unique and neat touches we're seeing on the G1.