I have feedback for you as regards retention of students.
The number one thing is due dates and late penalties. If I sign up for a course and work through the first few weeks and get everything done, and then I miss a deadline because life happens, suddenly I am no longer able to get a 100% in the class. I do not mind getting an A- in a class if it happens naturally because the material is difficult, but losing my A+ or A because I am 12 hours late on an assignment ruins the experience for me. I usually drop a class when this happens and wait for it to come around again.
A counter-example to prove the rule: Robert Sedgewick's Algorithms course. The last time he gave it, he had late penalties and I only had time to get through the first two weeks of the class without getting behind. This time around, there were no late penalties. Being enormously busy with other things, I was not able to keep up with the class as it went along. However, because I lost no credit for doing things late, I was able to complete the entire class in the final 10 days of course and I got an A. I have no problem staying up all night to finish interesting programming assignments and quizzes, but I need to be allowed to do this on my schedule.
I strongly encourage you to encourage your professors to do away with late penalties. It should be up to us as students to determine what our work schedule is. I know for some courses, those that use peer-evaluation, this is impossible, but many more could take this route than currently do.
I agree that Signature Track does have the effect of encouraging one to keep up with the class.