The big bus was a win for us. Rather than paying individual ubers or taking muni (city transit), we booked the big bus for the day. I do think it was worth the money. Before you depart, I recommend you download the app so you can see how far away the bus is from picking you up.
I almost gave this a 3-star review due to timeliness. They say "a bus leaves the depot every 15-20 minutes," and that may be true but it does NOT mean there is a bus arriving at your pick-up spot every 20 minutes. We waited 40, even 45 minutes, on a bus to arrive. We asked the bus driver and he gave us some excuse about traffic, etc.
Overall, I do recommend the Big Bus and would use it in another city to see the area.