Pros:
Close, convenient location to downtown Seattle. Extremely challenging for being on such a small plot of land, the holes themselves are designed very well. Usually very well maintained, a pretty little park with a nice variety of plant life.
Cons:
Biggest gripe: it gets REALLY crowded REALLY quick, also lots of rec. players--nothing wrong with that necessarily, but it slows things down even more. Being so small and cramming 18 holes into it, there are some flow issues (you finish in the middle of the park and have to walk through several fairways to get back to your car, for example). Also, a couple holes you shoot to a basket behind another one...can be confusing.
Other Thoughts:
The signature of this course, besides its small size, is the plethora of steel poles and nets installed throughout the park--resulting in lots of pings on bad throws. The poles are installed to protect the trees, and the nets to keep discs in the park. They weren't always there, and a lot of people gripe about them. Since I started playing after they were installed, they've never really bothered me. Metal poles are a bit of an eyesore, but they do protect the trees. And there have been numerous occasions when I've been saved by one of the nets protecting a teepad.
Although maps exist, its a good idea to have someone show you around, it can sometimes be confusing to know which tee to throw from and which basket to aim at. It's a cool little course, just try to play it in off-peak times.