Pros:
First of all, this is a beautiful state park. The course has its own dedicated area on the far side of the park that makes it feel like a disc golf oasis.
-27 holes. It's in every review, but this is the only 27 hole course within an hour's drive of where I live, so it's the only one I've played so far. The 27 holes are split into 3 loops of 9 that all begin and end by the parking lot, making it easy to play any combination of 9 holes you chose. I like to come on a weekend where I have time to play all 27, and have only played them in order, but you could play any 9, any 18, any tee, and have a new experience every time you play.
-Fairway combos. There's a great combination of highly wooded and more open shots. Trees are in play on every hole, but about half feature trees lining the fairway while half feature trees in the fairway. There are obvious lines on every hole, and I'm sure there are some fun local routes I haven't discovered yet (not on purpose, at least).
-The rough. As opposed to some courses that have extremely dense, punishing rough, most of the rough at Seneca is very much playable. I have yet to find myself in a position in the rough where I couldn't scramble and advance up the fairway. It's punishing, but a good scramble game will save many pars. I love finding creative ways to scramble, and Seneca allows you to do that without being overly punished. The rough is also not so dense that you'll lose many discs. I've hit the rough many times and not really been close to losing a disc.
-OB is well marked. There are strings lining OB throughout the course, which is a nice addition. I feel like a lot of courses only really line OB during tournament play, but the OB lines at Seneca are clearly and permanently marked, making it super easy to check your lie.
-Signage. There is a course map at the parking lot, and every hole has a very accurate sign showing all tee pads and potential basket locations. The hole signs also have a bead marking the current location of each pin. Even when you can't see the pin from the tee, the sings are accurate enough to pick your shot appropriately.
-Multiple pin locations and tee pads. Every hole has at least 2 tee pads (some 3) and 3 pin locations (some 4). I played 2 weeks in a row and some of the pin locations changed, so there's constant evolution to the course and every round will be a little different than the one before, which I enjoy.
-A nice hike. This may be a con for some, to be honest, but I enjoy the hike. The course is LONG. Playing short tees for all 27 holes takes me about 3 hours and results in a roughly 5 mile hike. There's lots of elevation change, but I love the hike. It makes the round fun, too. The last 9 holes are even harder when you're exhausted! There are benches at, I think, every tee pad. So even though it's long, there are many places to rest.
-Pro shop? Signs indicate that Innova discs are available for purchase in the park office. I haven't followed up on that, but assuming the signs are accurate, discs can be purchased on site.
Cons:
-Tee pads. The tee pads are mostly made of roughly 15"x15" concrete blocks. This means that over time and due to erosion, the tee pads can lack consistency and a lot of them are uneven. Since the long tee pads are used less frequently, a lot of them are overgrown, I've noticed. there are also some solid concrete tees and at least one is gravel. Just be prepared to throw from several different surfaces and types of tee pads.
- Layout. Now that I've played a couple times, I understand the layout a little better, but it was very confusing at times as a first-time player. Some signs show where the next holes are, but not every hole has that, so I got turned around and caught guessing a few times. There's also one point where you have to cross the middle of a fairway to get from one hole to another, which is not ideal. Just keep an eye out and don't be afraid to ask for help if you can't find a tee location!
-Bathrooms. There is one porta potty at the course. The park has bathrooms elsewhere, namely right before the main gate. I'd recommend stopping to go to the bathroom before you enter the park.
-Parking. Both times I've played Seneca, there was parking available in the lot. However, the lot isn't huge, and I can definitely see a situation where the course is busy and you have to park in overflow parking, which is available, but requires a bit of a walk to get to the course.
-Baskets. This may be a little nitpicky, but once I get up to the 4-5 star courses, I think that's necessary. The baskets are pretty old, and some are a little rusty. There are maybe 2-3 Chainstar baskets (I'm pretty sure they're chainstar but I could be misremembering), but for the most part the baskets are very basic and can result in some spit-outs that higher-end baskets would catch.
-Pars. Playing the short tee pads, I think this course being all par 3 is fairly reasonable. If long tees are all par 3s, I think that is a touch too difficult. I'd like to see some par 4s on a course with so many holes and so much space to play, just to add a little more variety to the round.
Other Thoughts:
The state park is worth visiting on its own merit. Lots of trails, a beautiful lake, picnic areas, boat rentals, playgrounds, and more. You could easily make an entire day out of coming to Seneca to play a round, pack a picnic, spend some time on the water, etc. The course is one of the best in the area. Remember to bring $3/person if you're a MD resident and $6/person if you're an out of state visitor (unless you have a state park pass). You will leave Seneca ready to come back and play again!