Pros:
Excellent design.
Elevation on many holes.
Technical and wooded.
Quiet, underplayed, great little park with camping.
Birdie opportunity on every hole, but the rough will punish you greatly.
Challenge, and fun factors are high.
Cons:
Carpet or gravel tee pads.
Needs signage.
Maintenance is difficult and unfunded.
Can be very wet during rain season, some holes might be considered unplayable by some due to standing water.
Rough can be brutal with lots of blackberry and stinging nettle.
Other Thoughts:
I love Waterloo and have been playing temporary layouts there since before there was a permanent course. This course is a classic Tom Embree design with assistance from Jon Owens and a massive amount of work from a small group of dedicated people over the years, including the Corvallis based Willamette Disc Golf Club, the Albany Disc Golf Club, the same small crew responsible for Bryant Park, Kirk Mcallister, and other locals. They have done an excellent job with few resources and little support from the Parks other than permission to install. This course was literally carved out of a jungle of mistreated and neglected forest in an almost completely unused portion of this County park. It is not exactly beautiful in a traditional sense but the woods is starting to reveal some of its beauty as the course and the foot traffic have opened up areas formerly choked off by blackberries.
The design of this course is a textbook example of getting every last drop out of what features the area offers. About half the course utilizes a big berm area, with the holes playing up and down the berm and in and out of the woods. The other half of the holes are mostly in the woods and feature a mix of length and technicality that force you to throw a little bit of everything. Virtually all the holes can be birdied with an excellent drive, but the punishment for missing your line will easily cost you a stroke or three, even on the more open holes because the rough on this course runs the gamut from stinging nettle patches, to almost impenetrable thickets, to dense woods. It makes for a very fun but still really challenging experience. You will not be punished unfairly, and in my opinion there are no unfair holes here. If you can keep your disc where it should be, and at Waterloo you can often do that with a controlled mid range shot, you will be fine. If you want to pull out your driver and go for it you will have a fair chance to get the birdie, but the risk is very present and will cost you. To me, that is the essence of great design.
The only thing preventing Waterloo from being one of the best courses in Oregon is the lack of good tee pads and signage, more regular maintenance and some beautification. The County Parks department does not have the funding or desire to improve the course and the disc golfers who have done all the work struggle to do what they can - and they've done a lot! Waterloo is further away from the bigger towns in the area and does not get the play that the Corvallis and Albany courses do and therefore doesn't get the attention.
There is currently carpet on 16 of the 18 holes, and gravel on the other two. The carpet works surprisingly well, and when wet provides great grip that is much better than typical rubber mats. It may not look great, but you will not slip. Basic wooden signs are at most holes, but other than hole number and distance they do not have much info.
I have not yet camped at the campground in the park but plan to do so this Summer. It looks like a basic, mellow, family friendly campground. Right on the South Santiam river with partially wooded sites, playground, picnic shelters, boat ramp and fenced in dog park, it is a nice little park.
If you are traveling through Oregon playing disc golf, Waterloo may not be on your list of destination course but it really should be. You can camp there and hit several area courses very easily, with Bryant, Adair, and Willamette probably the preferred choices for most. It is a very fun and challenging course that with a few improvements and more maintenance would get a 4 rating from this reviewer.