I have used the nurse rate many times. Depending on the time of year, the discount can be substantial. I would never advise showing up without proof, but in all the times I've used the discount, I've only been asked to show credentials once. (Come to think of it, it was on my first visit. Maybe they note past verification on your account.) Regardless, the discount used to apply to all categories of rooms. The last time I went, it was @ an additional $10 per room level upgrade (balcony, theme park view, theme park view with balcony, etc...)
Also, there is a web site that lets you check availability real time (not their official web site though--Google for it). Often, there are rooms available at Swan but not Dolphin and vice versa. Depending on the block of availability, it may be worth switching hotels during your stay to avoid rack rate as they are virtually connected.
