It depends on the context. When an undead creature can communicate pathos, it can be wonderful--one of my favorite moments in an old game involved the PCs' first confrontation of a simple, tied-up ghoul who had 24 hours previously been a drunk sailor on leave in town, and who was enraged with grief and hunger and begging them to let him free so that he could eat. He was no threat to the PCs at all, but they were pretty unnerved by him.
Statwise, they're no scarier than other creatures of their level. But they can be played for beaucoup unnatural points.
And yeah, Honesty_Algebra's art is fantastic: someone needs to hire her!
Daniel