A quick note for developers updating to Froyo 2.2. After upgrading my Nexus One to version 2.2 (FRF91), the Android Device Chooser that pops up when you try to debug your application indicates the device is an unknown target rather than version 2.2.
The Android SDK and AVD manager will indicate all has been updated (assuming you did that). The solution is to make sure you upgraded Eclipse with the latest version of the adb/ddms plugin. In Eclipse, go to Help->Check For Updates should take care of the issue.
An easy thing to overlook and my first check on Google didn't pull up anything. So maybe this will help someone else.
UPDATE: One caveat, only one usb port actually works for this. Nothing worked while trying to get the other USB ports working. I'll have to dig up another usb cable to try. There have been reports of some dodgy cables.