It seems like I'm missing a setting like that somewhere. In Settings, Applications, Development, I have USB debugging turned on. If there's an actual Use Debug Bridge switch somewhere else, please show me the way! This is crazy!

EDIT: Just for the logs. I had an old forked adb server process hanging around that needed to be killed. Once I killed it, the new adb is working just fine with 0.4.2 on my box.