I designed, built, piloted, taught and then oversaw FLEX Internet courses.  These courses were online open entry Math 1010 and Math 1050 courses.  A student was given up to 16 weeks from time of enrollment to complete the course at their own pace.  Many lessons were learned.  The biggest lesson learned (I already knew this but it was confirmed to me soundly) was students say they want maximum flexibility but they can't handle that much flexibility.  After some dismal results, I implemented bench-marks to keep students to a minimum pace.  I did have some resounding successes including a professional figure skater, soldiers in Iraq and Afghanistan and a pro tennis player that needed maximum flexibility and it worked well for them as they were highly motivated.  Because of the nature of what they were doing, they'd work during down time and then have periods where they couldn't do much but by the end they learned the material and did well.  However, many students would procrastinate and never catch up and it was finally determined that while the design and course was a good answer for some,  the amount of work it took to manually keep track of everything (the college was working on some automation for enrollment etc. but was never able to deliver) was not justified with the low success rate.