I wanted to like Big Bus, but they made it hard. It was difficult to understand when the bus would begin running for the day. Also, knowing how often the bus would pick up at each location was unclear, and that matters when it's 90+ degrees outside.
One bus we rode had no AC, so we could choose to sit in stifling heat in the shade of the lower deck, or in the blazing sun on the upper deck.
The audio tour was poor. It continuously started, then stopped, then restarted. And at times, the audio was referring to some building or monument nearby, but the bus was filled with standees that you could not possibly see what the audio was referring to.
Just not that impressed ...