Perhaps my tanks are not as stable as some as I do often move and changeup the plants, etc. and that does bring out the problems I see with eggcrate as a base. Plants will root very well in and around the eggcrate so that when I want to move or rearrange it gives me two options, neither of which I like.
One is to cut the roots off that are wrapped in and around the eggcrate. That leaves me a mass of roots under the eggcrate which die and add tons of waste to my tank. I don't want that!
But the second is even less welcome as I have to remove all the plants, totally destroy most of the tank and get the eggcrate up to be cleaned off which is also a super ugly thing to have to do.
I look at it as risk/ reward questions and just do not find enough reward. I've never felt the eggcrate plastic was going to do much if I drop a real rock that is big enough that I can't handle it.
No doubt that the type of fish I keep has a definite effect on my thinking as well, as I do often keep fish who dig and that leaves a really bad scene when they expose the eggcrate so that there is no chance of a "natural " look.