Pros:
I thoroughly enjoy Abner Longley, and seeing as it is the closest disc golf course to my home, I have played it a number of times.
In terms of pros, I would start by saying that this park is extremely well kept. Outside of the basket area of 13 (which is under tree so doesn't have a lot of grass and can get pretty muddy in the spring/fall), there are no regular "messy" spots on this course.
Another plus is there are two sets of tees, the "Pro" tees are concrete, and are definitely a challenge, not just in added length, but in many places, definitely different lines from the amateur tees, but the am tees are natural, so when things are wet these can get messy.
The baskets are great, and though there are no massive holes, (Holy 16 is 515ft I think from the Pro tees) this course offers a good range of shots and lines and also gives its opportunities to really bomb a drive.
Signage is great at each hole, and is clear and easy to understand.
Cons:
In terms of Cons, I would begin by saying when we have had a lot of rain, this course gets messy pretty quickly. Between the woods section getting muddy, there is a drainage ditch going running through the fairways of 4 and 5. Somewhat in play, but mostly not. Either way, when wet, flooding appears along the ditch as well as standing water in a few other spots around the course.
There are also no trashcans/water fountains/or bathrooms on the course. The park itself has a set of bathrooms on the playground that is near the basket of 12/tee of 13 which are open, and if there is sporting events going on (baseball/soccer) than the building after 16 normally has bathrooms open as well.
It has been mentioned before, but this is a multi-use park, with baseball happening in the summer, soccer in the fall both will effect the disc golf course. There are some permanent soccer goals up, but during the fall, the younger divisions get set up on the fairway of 16, so it might need to be skipped, and in the Summer 17 goes around a baseball field, and the errant throw into the outfield is pretty common, so this should be skipped as well.
Only other thing I would say, which doesn't affect me, since I play regularly, is there is no real indication of where the next tee is. I don't think it is tough to navigate, but there are some trouble spots where people might feel like they are wondering around blindly. (the transition from hole 6 to 7, the transition from 8 to 9, the transition from 13 to 14, and 14 to 15 as well.)
Other Thoughts:
Overall, this is a great course, one I am thankful I live close enough to play regularly. It might not be the best course in the area, but it is definitely a quality disc golf course for Central Indiana. For little to no elevation change, the designers put together an exceptional course that doesn't get boring and still keeps me coming back.