We have done it several times so obviously we think its "worth it.' You must provide your own transportation and it is very early, around 5am I think, as it must be finished before the water park opens.
We have always had great instructors. Two of the main guys have been the same each time we go. It is very exhausting, you carry your board back up from the wave pool to the top of the wave area. We have seen several kids get tired and quit or have to have an adult carry the board for them. Although there are plenty of lifeguards, you need to be a strong swimmer to truly enjoy the experience.
They do escort you out of the park if you do not have water park tickets for the day. Some people have arrived without rash guards and they did go get some but I would wear my own and bring your own towel. Observers are allowed in for free. There is quite a bit of paperwork so make sure you arrive at the designated time to not get behind.
We have always made the rest of the day a pool/shopping/movie day.