So why am I writing about it? Because we saw some very good reasons NOT to consider taking this tour and I felt those reasons would be helpful to others.
We were in Barcelona May 16 through 20th. I seriously considered using Barcelona City Tours but after a lot of research, decided to use the public bus system. And I'm glad we did.
We were lucky and had beautiful sunny weather. One morning we took the public bus to Sagrada Familia and, as expected, the area was mobbed with people. Plus, a bit of a bonus for us, the HOHO bus stops at the back of the church, which walking from the public bus stop took us right to the front of the church and an "OH WOW" moment as we turned the corner.
When we had made our way around to the back, the area was even more crowded .... with people waiting to get on to a Barcelona City Tour bus. There were company personal keeping things in order and people waiting patiently but, based on what we saw, it could take a wait of several buses before some people could board. Plus, being a bright sunny day, if you wanted to sit inside out of the sun, you would probably be out of luck.
We were glad we were using the city buses. We had stopped at an information booth and got a map of the city bus routes (excellent). When we told the information person where we wanted to go she marked the bus numbers for us. T10 tickets, good for 10 rides and shareable with everyone in your party, can be purchased at tobacco shops for 10 Euros. Transfers are allowed if the ride is less than 1 hour and 15 minutes. The bus routes you take are stamped onto the back of the ticket so you know how many rides you've used and what you have left.
Of course we didn't have the narration you would have on a HOHO bus. And if all you want to do is ride the city and get an overview, then, yes, go for the HOHO bus. But I wouldn't recommend it to get from sightseeing destination to sightseeing destination. For that, use public transportation.