While employed by many students and, surprisingly, recommended by many "experts," most college writing instructors actually discourage its use in university assignments. Surprised? Don't be. There are actually good reasons for steering clear of five-paragraph themes in most college essays.
They do a poor job of setting context. Since five-paragraph themes rely on an hourglass approach (general to detail to general again), it usually begins with vague, "dawn of time" introductions. In college writing, starting out with something concrete and giving ample space to a detailed background usually works better.
They make it difficult to construct complex arguments. Because of the strict use of space (e.g. restricting yourself to three points), five-paragraph themes are better employed for listing-style and descriptive essays, rather than ones that place heavy emphasis on analysis and interpretation. While it's possible, adopting another format should make the job easier.
They're too simplified for real-world situations. Look at the five-paragraph theme and try to find a real-world counterpart for it. Check out your favorite newspapers, magazines and, even, collected works. Chances are, you won't find anything that even resembles it. That's because it's essentially a dumbed-down style of writing. While it usually works for high school and, possibly, college freshman levels, most professors expect better from their university students nowadays.