I sailed on the Ecstasy in the beginning of March and am on the Paradise on May 12. The only difference in ship security that I could see (or was really aware of) was that Carnival had added the picture linked to your Sign and Sail card (don't know when they added that, but it was not done on the Fantasy when we sailed last May). and they double checked your id before you physically got on the ship.
I personally am not a worry wart, so worrying about security does not bother me. The only change I have made is that I re-did my air to Miami so that we could get in the day before so that we did not have to worry about airports shutting down because the screener was asleep or the machine was turned off of some idiot decides to carry on a plastic grenade or ...