Did this on a recent five-day visit to Bali. I've done lots of snorkeling around the world and even gone SNUBA diving on Kaua'i, so I thought this was a fun thing to do (especially since my wife doesn't care for any water activity with a snorkel in your mouth). The ups? (1) they deliver as promise, giving lots of fish swimming around you, (2) lots of staff to teach you and to escort you on your "walk", (3) all the facilities you could possibly want! It was a really neat way (albeit quick) to see the underwater world.
I didn't come out thinking that I would be rushing back, though. While they do NOT rush you through the event, you definitely do feel like part of an assembly line process. I understand that this is how they ensure that they make money, but it didn't make the activity feel special. Also, I didn't like how they give you food to attract the fish. It didn't bother me that it was nothing more than a couple of slices of white bread, but the fact that you carry it underwater in a plastic bag that I can easily imagine that numerous tourists lose each day when they do this. I don't have a solution for this, but with all of the problems with plastics in the water and on the beach I was constantly afraid I would add to it! (3) If you are looking to do this, try to do it first thing in the morning. With so many people going into the water, a lot of sediment is stirred up so the water was quite cloudy, even though we were going into the water around 10:30 AM ... I can't imagine what it would be like during peak tourism season in the afternoon after so many people had been there (this is not to dissuade you from going but rather to say it would be better to go in the morning, than afternoon.
So would I do recommend it? Yes, just know that you are getting what they advertised with only about 15 minutes in the water with your helmet on. If anyone from Bali Ocean Walker is reading this, I would recommend that your staff who trains the guests from the dive boat tell people that water is SUPPOSED to enter your helmet up to your chin from time-to-time. All three in our party admitted to panicking when this first happened and that if we had known to expect it, we might have been uncomfortable with it at first, but definitely would not have panicked!