I use it and have great success with it. Walleyes love it. I use main 3" black shad or white minnows. Catch alot of smallies on it too. I have great luck with it ice fishing too.
It just so happened that I took my new toy yak out for her maiden saltwater voyage this morning. I used Gulp about a third of the time. Nothing NADA.
However, a week ago, I threw some and quickly caught two nice fish (a redfish and a speckled trout.. both about 20 inches). So, I guess it works fine if the fish are there. If they are someplace else...doesn't help. Makes sense to me....Rich