Now there might be some of you out there who just can't wait to receive the upgrade. For you guys, there is a way to manually install the new firmware. First, download the software from Google's servers by clicking here. Copy the file to the root directory of your microSD card and name it update.zip. Now, turn your phone off.
While you are pressing your volume down button, turn the phone back on. Once you get the skating Android screen, scroll down to recovery and press the power button. When you see the /!\ symbol, hit power and volume up at the same time. You should now be presented with a menu. Use the trackball to scroll down to “Apply sdcard:update.zip” and click on it. When you see "Install from sdcard complete", select "reboot system now". The entire process should take about 10 minutes.
Let us know by posting in the comments box below, how the upgrade went and what changes you have spotted on your Nexus One. At 3.9MB, the upgrade is small is size which gives us the hint not to expect any big changes on the phone after installing it.
HTC Nexus One Specifications | Review