I have them on my '09 LT/Hannigan.
When I first got this trike, I noticed the floorboards stopped the impulse to put my feet on the ground when stopped. Don't even think about it now.
Like Rosy said, they do help keep the water off your feet in wet weather, but not a real selling point. I always use the pegs when mounting and tell passengers to use the pegs, so no advantage there.
I guess they do keep down the amount of road dust & debris hitting feet and legs for rider and passenger. And on long rides, they do provide an alternate resting spot for the feet.
So, are they worth the extra cost? I probably wouldn't pay for floorboards but I like the overall look of the bike with them and have no intention on removing them now.