Pros:
Beautiful well taken care of park with views of the Little Arkansas River and several old growth trees. Some tunnel holes (mostly from the long tees) and some teeboxes with trouble right off the pad which require precise accuracy to stay out of jail or OB. Cool over water shots on Holes 6 and 18. Challenging, yet not so extreme that it overwhelms you. Flows relatively easily although there are some trouble spots. Next hole indicator on the baskets rims (red and blue paint spots) showing the direction of the next tee box. Shady in many places, allowing DG'ers to get a little break from the heat. Hitting your lines can be key here and the jail situation inside the woods can vary considerably. Has alternating color tee pads, so you technically have four different layouts (short, red, blue, & long).
Cons:
Unlike its sister course Herman Hill across town, the pins are fixed so the only way to get variety is play different tees. No tee signs as the neighborhood park group won't allow them to be installed for fear that they'll detract from the beauty of the park. Layouts are shown with paint right on the teepads, but the elements are causing these to fade. Often crowded in the afternoon hours. 18's long pad and the retaining wall along side it (over the water hole) constricts your shot selection particularly if you don't have much arm. Parking area is small and there are no bathrooms (other than the woods).
Other Thoughts:
Originally a nine hole single tee course, Oak Park was expanded to 18 holes and given dual tee pads in 2005. Holes 8-14 are actually in neighboring North Riverside Park. The course is very popular with rec players and this can get burdensome on a busy afternoon. Best hit before noon if you can. There is also a busy sidewalk (on or over is OB) along the North Riverside holes so you need to watch for pedestrians.