Yeah, that coating does wear off, it's very finite.
As for the protector, to each their own. Considering the "retina" display, and the iFixit blurb saying how difficult it is to repair this, I'm using one. When the rest of this thing has scratches all over, I'll pull it, but for now, I'm keeping it. Besides, it offers a significant layer or protection in my application - one would be amazed at how much protection a thin layer of plastic provides when working with hard parts, and glass surfaces. That, and I have to wear gloves in this environment, and the bare screen is near impossible to use.
If you put them on right, not much in the way of visual degradation, or texture. The grease spots I'll give you, but a non issue in my case.
Besides, I paid all of 7 dollars for 2 (with free shipping), the 2nd one I'm going to use on the insanely expensive microscope objectives I've got kicking around.