As an Echols Scholar, I had fewer requirements than most students, but Echols status does not remove prerequisites. For example, needing a 200 level lab before taking a 300 level lab. For students who do have to have course requirements fulfilled, a common piece of advice is to take AP or IB. I don't know many IB students, but I took several AP tests in high school and know lots of UVa students who took them, too.
Pros to AP courses and tests
Advanced Placement classes are a great opportunity to get an idea for the rigor of entry level classes at four year universities. Depending on your college and test grade, you could even qualify to skip certain classes like Intro English Writing or Calculus I. Who doesn't want more free time in their schedule?
Cons to AP courses and tests
For the course, I can think of no downside. Students get great experiences from being challenged, and as long as you're not drowning in the material, there's no reason not to pursue these kinds of classes. The problem is in the tests. In my experience, they are not an accurate judge of how well students understand the material. I received a high grade on my Calculus test, but I decided to take UVa's Calc I course as a refresher. It was not a refresher. We covered more in that class than the AP class, and we went far deeper into topics. In other words, I would have been totally unprepared for Calc II if I had trusted my AP score, and in the Spring when I took Calc II, I saw a lot of people who decided to skip UVa's Calc I, and they were hurting. Similarly, a friend of mine passed his Physics AP and yet felt completely out of his depth with Intro Physics at UVa.
What does this mean for Dual Enrollment and other tests like it?
UVa is not a cake walk. Students can succeed here, but especially in math and science, you need to have a strong understanding of the material. I do not think that two years at a community college are on par with two years at a four year institution. I've seen too many people transfer in the Fall as 3rd years and leave after a year feeling overwhelmed. Some community colleges might have the same rigor; many do not, and it's not fair to people who think they are equivalent. AP tests, too, are less accurate than touted at predicting competency in an area. In classes that require a certain SAT II subject test, I have found that those are good markers, but I only have three classes on which to judge.
It's just something to be aware of when planning for college. Trust me, no one says their introductory classes were their favorites. They may have met great teachers, but people will still find a way to take fewer classes. My advice? Take AP classes if you can. If you get credit for something not in your major (for example, I got elective credit for history for my AP score), take it, but if it moves you out of something important (like math for a biology major), take time to think very hard about moving too fast.