We love to camp and hike here. This is a great park. It's dog and horse friendly, which I used to take advantage of when I had a dog. The park frequently hosts events that are educational and for all ages. The most recent event we attended was Acorn Day. My daughters (2 and 3 years old) loved it. Lots of crafts, music, food trucks, booths with animals. Very fun.
The only reason O'Neill doesn't get 5 stars is that it's located right next to the 241 toll road. It is such a buzzkill to be hiking down a trail and hearing cars rush by or find a smashed TV under the bridge. Other than that, it's great!
My friend and I went mountain biking on the trail here. It was a lot of fun. Several streams and small changes in elevation kept things interesting but, not really technical. A portion of the trail is 100% exposed for about an hour or so bring a hat or sunscreen.