I personally did not ride the hop-on hop-off bus in NOLA, but I bought the tickets for my MIL and my dad.
Initially, I thought it was a great idea for two seniors with different abilities since everyone can choose their own pace.
However (this could have been a bad day for the tour company, but who knows), busses were broken down, when told to switch to another bus, that bus had a flat - only to return to the previous (and then very full) bus. My MIL mentioned that she couldn't hear the tour, no one stopped to point anything out, and every bus prompted you for tips, and that with all the breakdowns the busses were too crowded to get on, and you had to continuously wait on a 3rd or 4th bus.
Sounded like a bummer to me, and was their worst NOLA tour experience that week, I felt so bad!