They lack premium products like Intel Extreme Edition powered systems with quad-SLI/Crossfire and no option for workstation cards like Quadro and Fire (have to buy it from the Apple Store
separately and pay a $500 premium over market value
). Not to mention the very limited selection (they offer no Fire cards from AMD and if the Quadro 4000 isn't enough, tough shit). They have above average products at premium prices.
Not to mention, they lag behind in product refresh cycles so, for example, their Mac Pro still has 3 year old graphics cards as the only option (HD 5870).