My impression was that the course was designed to give someone with little or no background in machine learning a maximally useful amount of practically relevan

My impression was that the course was designed to give someone with little or no background in machine learning a maximally useful amount of practically relevant information given a multitude of constraints (ergo the focus on Andrew Ng's favourite implementation tricks of the trade, learning curves &c.; each of dozens of such nuggets having the potential to save days, weeks or even months in real projects). If that was indeed the goal, the endeavour should, in my opinion, be considered an amazing success. An easy way to make the assignments harder (and maybe more fulfilling), if you have the time, might be to ignore much of the handholding (e.g. by porting everything to a very different programming environment). Ideally, online courses like that would be "infinite" and personalized, giving everyone as much depth (and breadth!) as desired (with a "baseline" approximately equal to the 2011 class) and taking existing knowledge into account. Eventually, we'll all get our Primer!