I was able to track my status beginning on April 13, 2011. Nonetheless, I received my I 797 notice on April 6th. So I would think that it took 7 to 8 days for USCIS to update my case status. But if you are unable to track your status online even after a month from your receipt date then I would suggest you to call USCIS and get the updates for your case. Hope this helps !