I kinda understand why people think macs still have one button, i mean they do have one physical button but multi-button mouses have came with macs for years and before that i would always replace the one button mouse with a multi-button track ball.
The mouses that come with macs today have a touch sensitive button. This way there is one button but the mouse knows whether your trying to left click or right click. They also have center click and side buttons. Goto system preferences, keyboard and mouse, and set up your mouse the way you want it. Of course all the buttons are programmable along with all of the F keys and what not.
Welcome to the world of macs, for better computer help with your mac check the forums at www.macnn.com or some other computer related site.