We drove to the national park on January 4th. Within the park you can visit Oheo Gulch and hike on the Pipiwai Trail.
The Oheo Gulch was really crowded. I had my wife and two teenage daughters and felt that we were bumping into people trying to get photos.
There were people swimming in some of the pools. We didn't so maybe this impacted the fun factor. We basically took the 0.5 mile loop hike to the pools, took some photo's and left.
We all made the mistake of wearing flip flops (that's a story for another day). I didn't feel that comfortable climbing across rocks to get up to the upper pools. There were some that did so I can only assume that with a little effort it can be done.
Personally for my family the Pipiwai Trail was the highlight of this stop not Oheo Gulch.