We purchased the 2 day hop on hop off tickets this week. We were told the bus would be every 15mins, but it was very sporadic, sometimes two at a time and sometimes 25mins between them, not easy to plan around.
Each bus stop was queued and with some stops we had to wait while two buses went passed us because they were already full, finally getting on the third one with only seats left downstairs. Long waits for all stops.
The commentary varied, some very good and informative, some very poor and just looking for tips all the time.
On the second day, we were trying to get a bus near the intrepid museum, but the bus route had changed with no warning, no update on the website or app. We suddenly saw a bus right outside the museum which it isn't meant to go passed. We managed to flag it down and get on, but felt sorry then for the people at the stops that were missed.
The app is very poor and a waste of time - the bus live tracking isn't accurate and doesn't reflect where the buses are at all.
Finally, and most annoyingly, you cannot get on a bus at any stop and ride the whole route! They sell it to you like this, but it's not possible. The buses start and stop at a certain stop number, so if you get on at stop 10 of 20 for example, you would then have to get off again at stop 20 and wait (and queue) for another bus, as they don't do a continual loop. Very annoying if you want to do a whole loop but don't want to start at stop number 1!
All in all, a bit frustrating and would only use it in future if absolutely necessary. City Sightseeing and Top View companies seemed to have much more regular buses when we were waiting at various stops and also didn't seem to have such packed buses - I would try them instead.