I like your double exclamation point at the end of your comment!!
I'll argue it's not harder to use in solutions -- I gave an explanation in the puzzle to open up the possibility, and it's a pretty short list of operands that are useful:
4!! = 8
5!! = 15
6!! = 48
7!! = 105
after that, the numbers get too big to be useful. I didn't find a use for 5!! or 7!!, but certainly there are more solutions I haven't found!