Considering Tonto National Forest makes an online PDF river map and a fold out traditional one... and National Geographic makes waterproof paper/tear resistant paper to print your own and a Salt River Canyon Map with mile markers and labeled rapids (also water/tear proof), I don't have a need for another salt map.
Nikwax also makes MapProof to waterproof regular paper/maps. We've had a map in a bottle of water in our store since 09 I think and it's still in great shape when we pull it out.
If it's under $5 and has an significant advantage over the other three, I might reconsider.
I just put in for permits tonight and can see having extra spots available out of the 15 person limit. I'll post if I get drawn...