Sure, you can create an extension set or separate boot partitions just for gaming, but that's an extra hassle and involves rebooting your machine. It's much better to keep your system folder mean and lean. With a game console, your computer can be busy doing something else. For instance, while you're downloading that 20MB demo of Starchild XI , you can be playing a game on your Playstation. Computers are built for work, not play.
Keyboards are well-built, but extensive gaming can ruin keys.
This may not be such a big issue with desktop machines, but the PowerBooks, it can be an expensive repair bill. Today's games aren't designed for computers anyway. One of the things that annoys me about modern games is the silly interfaces. Well, since most games are ported to many platforms, including game consoles that don't have keyboards, many games are designed to be controlled via a few buttons and a joystick. So next time someone you know is leaning toward purchasing a PC simply because of the game selection, tell them to buy a Mac and play games on something that's designed for it.