I use Nikwax Glove Proof on gloves that are half leather and half fabric. From my experience it works pretty well. I use Sno-Seal on gloves that are full leather. I don't use Sno-Seal on half fabric gloves because it will leave spots or marks in the fabric, I should also tell you that it will change the color of that natural tan leather. It will give the color a darker more worn look, which is actually pretty neat. With both products the water just beads off my gloves.
You'll need to re-waterproof them every now and then. It's not good for a lifetime.