i think it is definitely worth having. The little line you may see at times is a lot less noticable than all the rock chips you'll have splattered across your hood. I didn't want to spend the $400 or whatever it would cost for the expel when i got my car, but after having literally dozens of chips and marks across the front of my hood and front bumper, i really regretted not getting it. I just had my hood replaced after a minor fender bender and the body shop repainted the front bumper so I'm once again chip free and I plan on getting the xpel put on shortly.
i know someone who has a ggp like me and it isn't noticable unless you are close up and only then if you are looking at teh right angles.