I too have been searching for 6 months and I highly recommend doingit sooner than later. I have a few scratches - and I am insanely anal about my car! It is a tight fit to get a hockey bag in/out with the seats still up but I can and even though I "lift" the bag out - instead of dragging it out over the bumper - I still have a few scratches.
I have been waiting for 9 months for the stainless bumper protector (from ct200hchat.com) but they changed the status from "coming soon" to "...eventually"
I have looked online quite often and found a Lexus clear film one but now that I have some scratches I think I would most definately have air bubbles in an around the scratches and I have the Obsidian (black) color so would not look nice. There is one, I think on eBay, that is black rubber and I am almost positive I am going to get that.
As for dirt build up - it won't matter as I have never had a vehicle that collects dirt and dust on the back glass and bumper like the CT (and most have had hatches). Again my color is black so it gets dusty minutes after washing

but man is it bad on the back glass under the spoiler and on the bumper.