I would hold off upgrading to the 4 and wait for the 5, there will be more reasons to make that jump from 3GS to 5, October 4th is the expected date when apple will announce it at their event
I would hold off upgrading to the 4 and wait for the 5, there will be more reasons to make that jump from 3GS to 5, October 4th is the expected date when apple will announce it at their event