Environmental question - is any of this stuff safe to be using in your favorite fishing areas? According to their MSDS, off-the-shelf silicone sprays are 60% petroleum, 35% propellant (propane/butane) and 5% silicone.
http://www.wd40company.com/files/pdf/msds-3in16539428.pdf
Reel Magic is mostly petroleum
http://www.ttiblakemore.com/pdf/msds%20realmagiclube%20rml3.pdf
KVD Line and Lure - I cannot find an MSDS and I most certainly will not rely on the marketing propaganda from the web site. "It's made from a proprietary blend of non-toxic polymers. Why use sunscreen? Just spray on Line and Lure and get 100% UV protection all day!"
It seems that all of these products will make your line slicker and temporarily water resistant so that it casts a little bit further. Whatever other value they have is questionable.
And they are all guaranteed to empty your wallet.