Absolutely terrific.
The Big Island is, well..., BIG!!!
This tour just scratches the surface, but the operator has done a great job of collecting the greatest hits for a one-day jaunt. It's a long trip, no doubt, but our guide kept up a steady (and, for the most part, quite interesting!... :-)...) commentary that really helped pass the time, and had a lot of interesting relevant historical and touristic nuggets, to boot.
The point of this trip is to cover everything, once over lightly -- black sand beaches, waterfalls, volcanoes, lava tubes, desert, rainforest, and the magnificent views over the Wai'po Valley.
Do this trip -- you won't be sorry!