The attendant can take a long time at Serenity Bay too, and they don't have the excuse of having to keep up with 21 cabanas. We've buzzed for the golf cart on several occasions and not had it show up yet. That's why we always choose Cabana 22. Close to everything.
The family cabanas are lucky. At least they have the Concierge hosts working them. They know how to provide service. The Serenity Bay host is usually just some guy they got off of the boat. I've not had one yet who really knew how to help out except to catch you as you're walking back to your cabana from a bathroom break and give you a ride the last 100 feet.
That said, I like having a cabana because of the shade, comfortable seating, shade, refrigerator, shade, ceiling fan and shade.