Everyone's always talking about how shoddy it is and how your cabinets will disintegrate if they go through any kind of stress, but all my cheap-ass furniture with a piece or two missing is still going strong after nearly a decade a use. Maybe I'm just lucky and it really is all crap, but I can't shake the feeling that the reason people shit on Ikea is because it's inexpensive.
it's mostly that its all built with particle board/manufactured lumber. Everything that is "wood" burns hot and fast, but it all looks nice. Because it isn't regular lumber it is also easier to break than a normal piece of furniture would be made out of more traditional pieces of wood.
Their metals and plastics are generally fine though, you get what you pay for.