I will no longer be using Greg Mankiw's favorite textbook in my class, which I used myself as a first year college student 13 years ago and have used in every principles class since. I'm switching to Libby Rittenberg and Timothy Tregarthen Principles of Macroeconomics, which is published by Flatworld Knowledge. The main reason for the switch was that the new book is free online* (here is the free textbook). Of course if you want to print it or a paper copy it will cost you, but it will be cheaper than any other Principles text as a new book and close in price to used books.
The other change is I'll no longer be using Aplia, which is an online homework system. I liked a lot of things about it, they made things really easy for the professor. With Aplia and an electronic copy of Mankiw my students paid $80 a semester. I will now be doing home work through blackboard, which loses some of the nice graphing features of Aplia, but is also free. I can also use homework questions from Flatworld that I can import into blackboard.
So the question is with 70 students a semester at $80 each is this switch worth the $5,600 a semester (or about one student's tuition at Towson).
Will the students be better off? With money we could design an experiment where I use different books in my sections, then compare test scores controlling for student characteristics. If either publisher is willing to fund this experiment let me know. We would then have to estimate if the difference in learning if in fact Mankiw/Aplia are better is worth $80 per student, which would be hard.
Instead I think it will take a semester or two to see how students feel about the textbook and judge how they do on the exams, where I write all of the questions. I get no monetary benefit by switching and I have had to spend sometime switching my syllabus and will spend a fair amount of time getting used to the new homework system.
Over the semester I'll be going back to compare my new book to the old one and possibly a couple of other major textbooks.
* Opportunity Costs of free textbook not included.