What I usually notice from Wal Mart and Target (and other discount big-box stores) are worse veneers (thinner, easier to damage), greater likelihood that the product is already damaged out-of-the-box, much worse assembly instructions (less-clear, often with badly-translated directions that I assume were originally in Chinese or something), greater likelihood of missing parts, and (to borrow a delightful phrase from elsewhere in this discussion) terrible, coarse, void-filled "oatmeal cookie" particle board that crumbles if you look at it.

Ikea's stuff is crap (especially their lower-end items) but it's, like, good crap, by comparison.