Ohe'o Gulch is one of the major sightseeing attractions on a trip to Hana. When you have made all the way to Hana, it is surely worth to drive eight more miles. The Kipahulu Valley is part of the Haleakala National Park, and there is a Visitor Center at the parking lot.
Waimoku Falls Trail and Ohe'o Gulch are separated only by the street. A visit to Oheo Gulch is a stroll of 30 minutes on a paved way, while a hike to Waimoku Falls and back took us approximately one and a half hour.
Don't try to compare the number of pools with your guidebook. It depends on the amount of precipitation. After a lot of rain, the pools flow together, and you count less. It is common that visitors take a bath here, but you should be very careful if you try that.