On a steel heading trip, my seams failed on my brand new Orvis waders. That night while staying with a buddy, I noticed a can of the stuff and asked if I could use it. The waders had dried on the inside while hanging by a fire so I figured why not. I was torn at the time between voiding the warranty and fishing for the next couple of days. Fishing won, and I sprayed every seam. Next day, other than a few little leaks, the stuff worked out well. Those waders now though are used as my boat waders, but they still work well enough for launching and loading.
I also tried the stuff on the bottom of my pram, and that worked a bit, but it was not a permanent fix.