Endless things. You could write a book about all the things wrong with macs. You have to remember, this is yahoo answers, not a technology forum. A lot of the people on here are casual technology enthusiasts who don't really know what they are talking about. I sup[pose I could highlight on the main things. First of all, they are incredibly overpriced, sometimes contain equivalent PC hardware and yet costing twice as much. Second, they have a very small amount of third party support compared to PCs, you're going to have to put up with the Superficial Elitist Apple Team (SEAT) to get anything done. Graphics aren't high end, but that's because you don't play games on them. The Apple's Innovative security argument is laughable. For a computer to get a virus, someone has to write it. More people use PCs, so if I wanted to infect a bunch of people I'd write a virus that spreads via PCs. Mac users like to think that PCs get an exaggerated amount of viruses, but anyone who has the brains to install a simple anti virus program has nothing to worry about. Again, you could fill a book with all the things wrong with them, I would only recommend buying one if you are a complete noob when it comes to computers as OSX treats the user like an idiot. If you want a serious answer, go to a technology forum.
I am an experienced technology enthusiast, I build computers for a living.