Yeah, depending on what you want and what crafting skills you have. Special merchandise gives you access to a variety of craft-only items without having to invest in all crafting skills. MK IV grenades/mines, MK II incendiary/EMPs, gas grenades, focus stims and other craft-only drugs, etc. Also higher quality components and quicker access to rare stuff like W2C ammo blueprint. Also, once the next patch is out, merchants will offer less money for items you sell depending on the difficulty. Making money will be considerably harder on Hard/DOMINATING, making Mercantile even more useful.