I just had Busch Gardens Fun card (a cheap Annual pass for half a year) before I had a pass to Universal and IoA, and I have to say that Busch Gardens is the worst theme park in Central Florida. Some of the coasters are good, but besides from Rhino Rally (if it's open) and the coasters, they have mostly carnival rides. The park also is a lot bigger than IoA, but every thing is spaced out so much that theres not that much to do, and you could see everything in a half a day, but the lines might stop that. Most of the time, Busch gardens has unbelieveable long lines compared to Orlando area parks. Like other people said too, the employees are the worst. I guess they don't need to compete with other parks close by, since there aren't any so they let their employees act any way they want. It was rare that I would get more than a one syllable word out of a BG employee! The foods also bad. They have the same stuff all over the park, so you get bored with it.
I would defitly go to IoA. The rides are a lot better, the people are nicer (but not as nice at disney), and they have a version of Fastpass to keep the lines down.