Looking for opinions...
I've used the Nikwax in the past, and the results have been satisfactory--but my BM uses the cheapy spray from Walmart, and swears by it.
"Hope is a good thing, maybe the best of things, and no good thing ever dies."
"It's supposed to be hard...the hard is what makes it great!" (Jimmy Dugan, "A League of Their Own")
I've always used nikwax. Is the turnout expensive? If so, I wouldn't be willing to use another product that might not turn out so well. You never know what will happen when waterproofing blankets with different products.
I've been using the walmart stuff with the orange cap for years and think it works well. I reapply once a year.