We used them at Busch Gardens and Sea World in March and didn't have any real trouble. Some of the workers wanted to look at it really close, but it was more like it was their curiosity as never having seen one. Sort of like spotting a Yeti. Yeah, they exist, but I haven't seen one before.
On our first attempt at using the Platinum Passport on SheiKra we got out of our seats and asked the attendant for a re-ride. Don't do this, too much confusion for everyone involved.
They prefer (and you will too) if you just stay in your seat when you get back to the station. They generally don't open the gates to let riders on until everyone has disembarked from the coaster. You'll attract the attention of a ride op and you'll show them your pass and ask for your re-ride then.
We mentioned the "Florida Platinum re-ride" while our restraints were being checked and asked "Should we just stay in our seats and show the pass when we get back?" The answer was always yes. It really is too confusing for everyone if you get out of the seat and try to do it after the fact.
The cool thing is this works for any row you're in, so if you waited for the front/back row of Kraken/Montu/Kumba/SheiKra/Gwazi you stay in the same row. The Quick Queue people can't even do that. The Platinum works for Journey to Atlantis and our experience is that you have the entire boat to yourself on the re-ride.
I don't know if they'll honor the re-ride for Manta. For the price we paid, I sure hope they do. Since they're giving all passport holders a 8-9a access to Manta before the park opens until Jun 30, I can understand that they wouldn't have implemented the re-ride yet.
We'll be there the second week of June and plan to take advantage of the early opening a few days, but won't be dissapointed if we can't re-ride (ok, my son will be disappointed, but such is the life of a 9yo boy).
Let us know what happens.