Using regular shoe polish on Gore-Tex footwear might be a bad idea - some of the brands out there might block the membrane. Here's a safe bet, and made by HAIX, too.

Modern membrane shoes have usually two layers of leather. When you apply polish to the upper layer, the polish might soak through the first layer and through the second protective layer onto the membrane itself. This is bad news as a regular polish will usually end up clogging the pores, creating a membrane that doesn't let air pass trough. Polishes made for membrane shoes (like Gore-tex) have substances in them that wont clog the pores if it comes into contact with the membrane. We don't know what those substances are called, probably something pretty fancy.

To drive home the point: use polish made for your shoes. That way you won't end up with expensive rubber boots. You know you're getting your moneys worth when it says 'HAIX' on tube. As an added bonus it works with regular leather shoes as well, although let's be honest, you should use the cheaper stuff on them.