It's also one of the most conceptually difficult parts, which makes it a good learning opportunity.
One common criticism of compiler classes is that the first semester spends all of its time on parsing, so the students don't learn very much about compilers. And btw, there's an infinite number of conceptually difficult parts when it comes to optimization.
"It's also one of the most conceptually difficult parts"
... except all the others.
Conceptually? I'd say it can be tedious, if done by hand, but the concepts are pretty simple.