I'm most interested in the leather loop and metal bracelets. SS is usually pretty heavy and I'm surprised there's no liner for the inside of the leather straps. Might be a problem with staining while exercising.
Apple indicates that the leather bands aren't water resistant so if you plan to exercise with the Watch on, grab a Sport band when you pre-order. Another $49 is nothing if you going to shell out $549-1049 for the SS model.
However, if you don't feel like swapping out bands you can consider the link bracelet (if you can handle up to another 65-75g depending on how many individual pieces you have).