Can I use this on synthetic surfaces, like a toe cap?

I use it on the whole boot, so some gets on the toe cap. It has not changed the color or damaged it in any way.

Would this be good on some bogs rubber boots?

I use this on Kennetrek boots as they make the boots and they know exactly what will not deteriorate their boots. Kennetrek boots are not cheap and I would put nothing on them that would ruin their performance. I used my boots out west this past winter and they are the best winter boots I have ever had!!

Does this smell any different than Obenauf's?

Yes, our boot wax is made with natural ingredients that are different from Obenauf's and has a milder odor. In addition, do not use products other than Kenetrek Boot Wax on your Kenetrek boots, or they may be damaged.

Will this change the color of your boots once applied?

This product, right out of the can, is clear. This product is not a dye but a conditioner & waterproofing. It will change the color but to protect, condition and waterproof leather a slight change in the the consequence to proper boot care. This is one of the best boot/shoe care products I have ever used. If you are deeply concerned, only apply an VERY SMALL amount on your bare finger and gently rub It into the surface at the backside and near the sole of the boot. Let it dry and see what you think. Application of the product, in my opinion, creates a deep luster to the surface, enhancing the out-of-the factory color on the surface of the boot. Leather, an organic material, must be conditioned regularly (think monthly or quarterly) or the leather will crack and degrade. I never use polish on any of my shoes or boots, but use conditioners and on occasion dyed boot creme if I have been negligent in wearing them and an errant abrasion occurs, which is rare. I think you will like and use this stuff once you try it.