It can be fun, and it can be frustrating.
Site quality determines that in part. So does how tired I am!
Frankly, even though TEPaul touts the "open bottle" method of routing, I find if I am tired (may have been hung over in younger days, now, just old....) I find I can work on grading or green design. Somehow, the routing process, if tired, just goes into a logjam, where I keep coming up with the same ideas - with the same flaws. In the trade, we call it "designer's block." Somehow, that just doesn't happen in feature design as much.
But, on a great site, routing is a pleasure. Even a bad one, or one with housing can be enjoyable. The worst are the ones you suspect will never turn into a real golf course, and all of us have done plenty of those!