Pros:
Fairfield does an OK job of utilizing what they have to work with. It has some nice elevation changes, some longish shots and a few tight wooded holes. The course is very popular and has done a good job of promoting the sport in that area. When the wind is blowing it can present a good challenge of your skills. There seems to be a good variety of distances and uphill/downhill shots. The swamp is used for a pretty good risk-reward shot on hole #10. At least I think it is hole #10, there are no tee signs so it is easy to lose count. Given that many of the Chicagoland courses are short, flat 9-hole courses, the elevation changes and distances makes it a very good course for the area.
Cons:
A lot of the course is set on a completely open hillside. Holes 1-5 & 11-12 and the alt shot using the practice basket are completely open with not a single tree in the design. Holes 6, 9,13 & 18 are mostly open. That's 12 out of 20 shots that you basically grip it and rip it with only wind and elevation changes adding to the challenge. It gets pretty repetitive and boring. The fairways on these holes are mowed with "rough" to the sides, but there is no penalty for throwing from the rough. It does make it hard to find shots out of the fairway, which backs the course up frequently.
The course has no tee signs. The mowed fairways lead you from hole to tee, so it's relatively easy to follow the course but you have to judge the distance yourself. The tees themselves are natural and are in disrepair. There are blocks to mark the actual tee, but huge areas of compacted soil surround them making them hard to find on many holes. In wet weather they are huge mudpits.
The some of the wooded holes are really tight, # 7 in particular. This adds to the "lost disc" problem and helps back the course up further. In general the wooded holes are pretty nice and they have trash cans with the hole number painted on them. Due to the lack of tees, it is easy to lose track of how many holes you have played. The "14A" shot needs to be cleaned up, at least weed-whacked. I could swear I have heard banjos playing back there after I trailblazed my way through the downed trees and knee-high weeds on that hole. If someone would hide back there and say "I bet you can squeal like a pig" I would scream and run for my life!
The extra hole between #11 & #12 that shoots back to the practice basket is confusing. Because there are no tee signs, there is really no way for a first-time player to know it's going to take you to a dead end at the parking lot and you will have to walk back down the fairway to play # 12. If you play that hole, you are likely to either have someone shooting at you as you walk back down the fairway or encounter a back-up at #12 once you walk back to that tee (possibly both.) IMO that should remain a "local" hole and the fairway should not be cut to help players know which way they are supposed to shoot when they reach the tee area for those two holes.
Other Thoughts:
All-in-all Fairfield is a pretty good course compared to other courses in the area. If you are a Chicagoland-area player it's a pretty good choice for a course to go to. However, it is not a very good course when compared to other courses around the country, which is how I rated it. I can see why a local who has never played outside the area would regard this course very highly, but looked at from an overall perspective it has too many open shots, no tee signs and terrible tee-off areas. Those factors have to figure into the rating. Despite the loyal following it has from the local disc golf scene, I'm afraid travelers from out of town will be disappointed in what this course has to offer.