I don't blame you Ravi. I've been waiting for 4ish years myself and I know the feeling.
Anyway, here are the examples,
Most common, (This gives you a chance to fightback).
A written decision in this case was mailed on November 26, 2002. If 14 days have passed and you have not received this notice, you may wish to verify or update your address. To update your address, please contact the service center where you submitted your application during business hours.
Another,
On November 21, 2001, your I485 Application to Register Permanent Residence or to Adjust Status was rejected as improperly filed and was mailed back for correction. The specific reasons are explained in detail on the rejection notice mailed with the case. You can refile this case, after you have corrected the problems.
And what we don't know about,
On December 12, 2002, the document we made based on the approval or registration of this case was mailed directly to the person to whom issued.
So it seems .. this just might be an approval (looking @ the wording), and please do let us know ur details if this does turn out to be an approval.

good luck.