On the island of Tahiti, there really isn't much "off the beaten path", cause they just aren't that many "paths".  We did rent a car and drive around the island, which was nice.  If you go nonstop, I'm told it takes about 2 hours, making stops it takes about 4 hours.  There are a few nice lookouts along the way, and a few waterfalls you can drive (almost) up to.  One of them requires you drive for about 15 minutes up a rather poor road, but upon arrival, you can park your car, and it is an easy 5 minute walk to see the falls, which are quite high and quite spectacular.  We were a bit disappointed in the Gaugain museum, (no Gaugain paintings there), I think only a few original sketches.  There was a nice restaurant nearby, right on the water. 

They do have very expensive tour buses that go around the island, I think about $150 per person, but you can rent a car for the day for about $140, automatic.  There is basically only one road that goes around the island, so it's quite easy.