Having just got back from Universal a week ago, I can help.
As others have mentioned, if you are a AAA member, show your AAA card whenever you purchase food or souvenirs and you get 10% off
Meal plans are a great bargain here so take advantage and purchase it!
As for Harry Potter....

IT'S AMAZING!!!
Downside to Harry Potter? The wait times.

My friend works at Universal and they are not expecting the crowds to die down til at least next year.
We arrived at Islands of Adventure the minute they opened (9 am) and headed straight to Harry Potter. The line was already all the way back by Toon Lagoon.

So you stand in a long line and a guy comes around passing out tickets and once he runs out of tickets, that means they are at max capacity and no one else is getting in. By 10:30 am, HP was at max capacity.
The wait times were as follows:
1 hour and a half to get into the Wizarding World of Harry Potter.
1 hour and a half to get onto the forbidden journey ride.
45 minutes each for dragon challenge and flight of the hippogriff.
close to 2 hours to get into EACH of the stores and the three broomsticks restaurant.
30 minutes for butterbeer. (get it frozen!!! so YUMMY!)