Pros:
(Rating of 4 is based on how it's playing right now, a solid 3.5, with a .5 bump for the steady progress in development.)
I've been playing this course for some time and it just keeps getting better. I agree with other reviewers that one of it's best features is the land itself, but it's also how the designers have used it to create some really great golf. Each hole is unique and the full 18 requires a broad range of shot making from drive to putt: right/left/straight, uphill/downhill/cross slope, low/high ceiling, water hazards, etc. Its laid out well so there's no criss crossing fairways or long walks between holes (there is one slight walk back from 16 to 17) and play begins and ends right at the parking lot.
While most of the holes are in the woods and were frustratingly wooded when all 18 were first put in, they've been cleared out gradually for more open fairways. Now there's more playable area and some fantastic shot lines. The holes which do involve field shots--1,5,8,17,18--are also being opened up, giving more relief from the trees. Some of the baskets/tees/fairways which used to play too close together have been worked out. Another great feature, which helps give the course variety, is a stretch of holes on the back nine--12,13,14,15--which play along and over a really nice creek. These holes have a ways to go in overall maintenance, but each plays the creek a little differently and include some of my favorites on the course.
Recently all remaining baskets and tees were installed. The choice of wood chip for the tees is debateable, but it does fit the character of the course. If they harden over time and are raked and leveled regularly they should be fine. I actually don't mind this variable as part of the challenge and uniqueness of the course.
Another thing I've come to appreciate (especially with the heat this summer) is that because Darnestown is mostly in the woods and plays along water for a long stretch, it's the perfect hot weather course.
Cons:
Little short: Overall course distance is on the short side. Looks like there may be a few holes which can be lengthened, but otherwise it will always rely on obstacles and terrain to provide difficulty.
Gnats: Much like Seneca can have a lot of gnats. I've played at all different times and in the late spring and summer months you can expect them, so plan accordingly. In the fall, winter and early spring it's typically not an issue.
Natural wood chip tees: These were definitely unstable when recently installed. Hopefully they'll tighten up. Some tees are shorter then regulation length, but it looks like there is room for these to be lengthened.
Lacks signage: I've played the course enough that I don't need signage, but this would definitely be lacking for the first time player.
Private club: During the middle of the day in the summer months the tennis and swim club can be crowded. And while I've played at these times without any issue, it still feels a little uncomfortable. Not sure what the situation is for the parking lot gate exactly and parking along the road seems less than ideal for the neighborhood, but again no problems so far.
Other Thoughts:
Not only is Darnestown a nice compliment to other great courses in the area such as Seneca, Patapsco and Rockburn, but if progress continues as it has in its first few years, it could be grouped with these for some of the best disc golf in the DC Metro area.