Pros:
As with all the Michigan Metroparks, the course has great signage and tee pads. Also, the fairways are mown tightly.
The biggest pro with this course is that it is very challenging and will give your game a very complete workout. Most of the holes are moderately long, so power comes into play, but only if accompanied by accuracy and smart shot selection.
The course has some very good holes as well as a couple par 4's.
There are many points where choices need to be made, particularly in regard to how hard to get on the throttle.
It's likely that you'll not see any other park users during a round and the wooded seclusion is very attractive.
Cons:
Willow does have significant drawbacks, however, as the previous reviewer has pointed out. The course is a bit of a beast and I think would be best as an 18 hole layout, instead of 24. This is particularly true in light of the fact that many holes are redundant in terms of design.
Although I prefer tight, technical courses, I feel that this course takes it too far for 90% of players. Many of the holes could be greatly improved by removing a few trees and widening the fairways at key points.
Particularly in the summer months, the schule can be very nasty. Some blind shots, coupled with the schule can make for lots of time hacking through the brush looking for discs.
A lot of the time the course can be quite swampy and full of mosquitoes. The months when you have the best chance of a good experience are only May-June and September-December.
Other Thoughts:
Remember: Don't be a dirty disc golfer. If you pack it in, pack it out!