Pros:
I really like courses that use two pins and two tees well. Giles Run does just that. Each of the four layouts provides a new way to play the hole rather than just adding distance. Unfortunately, I only had time to play one layout, so I chose to really test myself on the longest layout. The long layout features a number of well laid out multi-shot holes that can challenge even the best while the shorter layouts provide some relief for less skilled (or less masochistic) players.
Although the course is mostly open, it uses the available features (rolling hills, tress, and yes, thorns and thick brush) to set up some interesting shots. The course really never feels especially repetitive.
Cons:
There is one consistent feature that seems to steal the headlines at Giles Run: impenetrable, thorny rough. It's not just the thorns that cause problems, it's also the sheer density. This is some of the thickest rough I have ever encountered. It's not enough to know where your disc landed, if you want any hope of retreiving it, you have to figure out how to get to it. We even sent spotters ahead on especially risky shots. I had one land no more than 10 feet from where the spotter was standing. He was able to point out exactly where it landed, and where it will likely rest for a very long time. There was absolutely no way to get to it.
Playing from the rough is an important aspect of disc golf, but Giles Run takes that element of the game largely out of play.
The fairways are certainly fair, without the rough encroaching too much. But none of us are immune to bad shots, and the risk of losing a disc is present on nearly every shot at Giles Run. This can change the mentality of the round, where the thought process is more about keeping discs in your bag, rather than trying to hit a nice line. This takes a lot of the fun out of a round. With the distance, fun elevation change, and relative openness, this would be a really fun course to play super-aggressively, particularly in casual rounds where score isn't as important. But if you're playing with discs you're at all attached to, conservative is the way to play.
Navigation can be tricky for first timers. Hole 7 is tucked away behind the pond by itself, and then the long walk to 8 has no markings to assure you you're heading in the right direction.
The signage also leaves a lot to be desired. A few holes had map and distance info, but most have only the hole number marked. Especially on the longer layouts, where the basket is often not visible from the tee, more info at the tee would be really helpful.
Other Thoughts:
I really want to be able to rate this course better, but I have to settle for a "good" rating. The layout is really done well, but when the signature element is the rough, it's hard to give the course more credit.
Be prepared, bring a map, wear long clothing that you don't mind getting a few tears in, and use discs that you're not especially attached to.