Ok, actually, from talking to my mac fanboy friends, the game doesn’t work too bad but they mainly have REAL PC mice with mousewheels and etc…
Here’s a funny snippet from the Steam Forums.
MacUser: “How do I select the other portal”
PcUser: “Mouse 2”
MacUser: “I only have one mouse button”
Photo Source: http://www.goopeg.com/img/ZsXg0uHn.jpg