For instructors and students, using Aplia is a great way to reduce the cost of teaching and learning. The chapter assignments in Aplia are easy for instructors to assign and help students to get a grasp of the material in a way that traditional sets don't.
If students see Aplia as a substitute for other methods of learning, such as reviewing lecture notes or even just attending lecture, then student effort may in fact go down. However, if students see Aplia as a complement to their other study methods, then their effort—and consequently, their understanding—will increase.
How can you, as an instructor, help your students view Aplia as a complement to their other efforts to understand course concepts?
The easiest way is to integrate work on Aplia into your lecture plans. When I taught using Aplia last term, I picked one Aplia problem for each lecture, based on the reading for that day, and made it due 15 minutes before class. The object of having them do this problem was not evaluative. Rather, I assigned it so that they would come to class knowing, in their own mind, what the general subject of the lecture that day was going to be.
By starting out lecture with something familiar, I found it to be much easier to move them along to new material, since their heads were already in the right place. The act of doing the problem and the act of sitting in class were explicitly complementary, since I designed them to go together. And when my teaching evaluations came in, I found that the students singled out the pre-class assignments as the single most useful thing in helping them understand the material.
The flip side of this, of course, is that you need to be sure that students don't see Aplia as a substitute for other kinds of effort. The easiest way to do this is to stress that the exams you give will not look like Aplia chapter assignments. Give them practice tests, or extra problems based on your lectures, outside of the Aplia framework. The important thing is that the students realize that doing one's Aplia assignments may be necessary for doing well in the class, but it's not sufficient.
Just like breakfast cereal is meant to be "part of a healthy breakfast," Aplia is not designed to be consumed alone. It's meant to be used in conjunction with the traditional methods of teaching and learning, not to replace them.