[Quickurt]

I love the stuff for all the vinyl on the Boxster. My only complaint is it obviously does what it is advertised to do, replace volatiles from the polymers. The loss of monomers from the vinyl, through evaporation, is what literally dries the material out and makes it shrink, crack and deform. UV degradation is the other major contributor to the same effect, and I'm surely not expert to say which is worse.
The 303 replaces the monomers that evaporate and therefore are there to evaporate again. This puts a film of same monomers on the inside of the windsheild to now be cleaned!! Let's just hope Windex doesn't add another problem to the viscous cycle!
The other big point of 303 is UV protection, so it's also sunscreen for your dash and other vinyl.