Let's start out with the fact that the outdoor portion of these gardens were free. Yes, free. The indoor conservatory portion cost us $2.00 per person, which I gladly paid, not because the indoor part was spectacular, but because we wanted to support the whole place.
We had just dropped off someone at the airport and wanted something to do for a couple of hours until their plane left. (make sure they took off ok). About 10 minutes away was the Olbrich gardens.
As a visitor, the grounds were scrupulously maintained. The conservatory was nice, with tropical plants, a waterfall and a few butterflies left. There were 15 outdoor gardens, with easy walking paths. We spent a couple of hours wandering through and no one was bored.
If you like theme gardens and are in the area, go.