From one of my students:
>> Do you like exercises like this, or should we just stick to the stuff in >> the books? > Both. But I like exercises like these more because stuff that's in the > book, I can do on my own when I have the time. Stuff like this is > different, and interesting.
I should keep that in mind. =) Stuff that's in the book I can suggest for practice, but in class, let's do something unusual and useful.