For those who were granted deferred action and obtained EAD, and then obtain a SSN, do not forget to transfer your credit history (if any) to your new SSN, and also update all your financial/education/etc. institutions about your new SSN. Lastly, you are required to rescind your ITIN once you obtain a SSN.
Here are some helpful links:
transfer credit history to new SSN
http://www.ehow.com/...signed-ssn.html
rescind ITIN
http://www.immihelp....etting-ssn.html
also for men, you have to let the Selective Service know about your new SSN
http://www.sss.gov/default.htm