If you do not have Tiger yet, and you use an Airport Extreme, do NOT update. Tiger and the Airport do not get along. At random times Tiger will lose it's IP addresses, and you will have one hell of a time trying to get back on. Its always kicking me off and refusing to let me back on, and I have to reset the router over and over, restart my computer, etc, and eventually it will just decide one time to let me back on . . . . . until the next time it kicks me off. Stay away from Tiger until 4.1 comes out. This makes me sad, since I've been looking forward to Tiger and using Mac's my whole life BECAUSE this stuff doesn't happen to them.