Pros:
Hidden down the stairs (or the land shelves if you find the original entrance) from the original Rosedale course lies a shorter course with some of the most heavily-wooded technical play you'll come across for a sub-5,000ft course.
The way the ruggedness of this course hasn't been replaced with the modern concrete tees and color tee signs just adds to the experience. No, it's not Diamond X, but dirt tees, 8-inch long pieces of 2x3 with the hole number painted on them, and bright orange Kingpin baskets with a slight lean to them are all marks of an older, but still well-loved course. 1, 4, 8, 10, 12, and 17 all have multiple tees.
Besides the obvious "every hole is heavily wooded" aspect, elevation is abundant and extreme! Hole 2 is a drop of at least 40ft to the pin, hole 15 is back up about the same distance (when's the last time you played a 183ft hole that played like 300?), 11 is fairly flat up until the last 50ft, where the land suddenly jumps 10ft upward to the pin. Hole 5 is a blind uphill, which slowly moves left and back down once you crest the peak of the rise (maybe 8ft up off the tee, just enough to hide the basket). I'm only mentioning about half the holes with the extreme elevation but it's enough to give you a picture.
While difficult, the line is always present, and often there are multiple lines! Those are almost always welcoming to a forehand or backhand, but you will need both to be working well as the pin spots are usually a very fair balance of right- and left-finishing shots. There are several risky putts to be had. Maybe not the best type of risk-reward because on some of them there's also lost-disc risk (5 and 13), but yet another added challenge factor.
The entire course is well-shaded. On a hot day it will either keep you cool, or trap all that heat under the leaves and slowly cook you.
Cons:
Steep dropoffs next to several different areas of the course. 1, 4, 5, 13, and 14 are on the edges of the park and their right sides all have a long way for a disc to go, while 6, 7, and 18 all border hole 9's fairway and it's a steep, plant-filled slope down to it. The same goes for 15/16 filtering onto 14/13 on the left side, respectively. If you want to score well, disc down and keep it on the fairway.
Foliage in the summer is really rough, especially off the fairways. It's hard to do maintenance on a mountainside, but it's something to be wary of.
Navigating is more difficult than most. Finding the beginning of the course, the end of the course, and the run of 10 to 11 to 12 to 13 is tough even with the orange app. (I played with one of the guys who helped install the course and we still got lost from 11 to 12!)
The dirt tee boxes can get really rough toward the end of a season. One bad x-step could leave you limping for the rest of the round. And the course holds water pretty well after a rain, so give it time to breathe after a storm. The paths between holes (and even on holes 9 and 10) can get a little iffy (and steep), but the more regular use is beating those paths in to be safer than when I first came through.
Other Thoughts:
From the course where the stoners could go have a smoke and a round in peace, to a now well-loved and cared for course, this is a reminder of earlier days of disc golf. Everything's a par 3, pack it in/pack it out, and most fun wins (or is it fewest lost discs?). The regular changing up of pin spots makes return trips worth it. I shot +5, then came back four months later and shot -4. It's an adventure of a time.
You'll notice I didn't mention any bad holes... because there really aren't any. Maybe hole 1 is a little short and flat? Maybe 17's green being perched on a hill isn't ideal? Maybe 8 is too easy? Maybe the course overall doesn't have enough long holes? Any of these gripes are outweighed by the other amazing holes on this course. You should always be able to walk away from Down Under with a memory of a new, unique hole, plus a shot or two that you're very, very proud of. And there's a whole 'nother course on site with two baskets per hole!