I couldn't agree more. I can take a C for about one-fifth the work of an A. I'm usually interested enough to explore the interesting material at depth anyway. I just don't do every tedious assignment.
So yeah, it's a lot easier to get a C, and it's possible to get a C and have full knowledge of the material, but it's also very easy to _think_ you have full knowledge.
I'd aim for a B, not a C. If one really understands what's going on that shouldn't be tough to get, and it will give a GPA that won't cause some employers to turn an employee away. A student is more likely to actually know what class they took if they at least got a B.
That said, I think the mentality that you only need to do the requisite amount of work to pass can be pretty dangerous. Sure, you may think you understand the course material without having to do the work, but just like with startups, the devil is in the details and the actual execution is what matters. If actually doing the work wasn't crucial to the learning, why not just read over and think about every programming assignment for 10 minutes without doing the actual programming?
I also wouldn't say that my approach is doing "the requisite amount of work to pass." Classes inherently have a lot of fluff, a lot of which doesn't really teach you anything. Take my software design class, for example. There were a few core concepts they pushed heavily and I learned those well, but I already knew the small implementation and GUI details. I could have spent the time building those out and getting the A, but I'd much rather take the time to apply those details to my startup.
It turns out that learning what I felt I needed to learn earned me a B in Software. It's different for every class, but I think it's possible to both pursue a startup and get your money's worth out of school. Unfortunately, it's often your grades that take the hit.