ive used rain-x on the windshield and rain-x wiper blades and i dont have a problem..and it rains all the time here in florida..but one of the main problems here is the pine sap gets on the windsheild then causes that one spot on the wiper blade to either bend or wear out faster then the rest of it so by the time i get that little spot of sap off the windsheild the blades are screwed and then i have a constant line of water

and no not all wiper blades are the same..different cars take different lengths...i think there are 16 inch all the way to 24 inch if im not mistaken...wherever you go they should be able to tell you what length that and in your owners manual it tells you what length