It wouldn't be a bad idea to use both. It could be nice to study a monolithic kernel-based OS (xv6) and a microkernel-based OS (MINIX). In 6.828, we read xv6, and we implemented parts of JOS, which is exokernel-based. Since exokernels are kind of like microkernels on steroids, I suppose it makes sense that we didn't focus on normal microkernels too much.

A different way to put it is that they used the data to explain why Germany was the favorite. Which seems pretty cool to me!

Definitely. For anybody interested, http://mitpress.mit.edu/sicp/full-text/sicp/book/node90.html offers a nice introduction to the amb operator.

One issue that I found when solving problems like this is that, to achieve speed, it can become necessary to use many nested lets. That could hurt readability. Nobody wants to see a line of code nested 20 tabs deep!