I'm able to use my laptop both with and without a mouse - though I do prefer having a mouse, and I've known about the middle mouse button for many years now.For me, it depends on what am I using the laptop for. If I'm just browsing or working on an assignment, I prefer using the trackpad. But for gaming, I will use the mouse, because it's difficult to play TF2 using the trackpad
I usually prefer using a mouse, but I will use the trackpad if I'm just browsing the web and have no mouse pad or suitable surface for an optical mouse. But for gaming, a mouse is definitely a must.