It actually has a ton of buttons, lol.
Right click, left click, middle click (wheel), 2 buttons on the side (configurable) and volume up down and mute buttons. Personally, I've configured the middle click as just that(use it to open new tabs in safari/ff/opera, i'm a tab whore), have turned off the 2 side ones, and rarely use the volume. The buttons aren't annoying or anything, though, not a worry. Just know that someone left handed will NOT want to use this set up, it's super-ergonomic for righties