I work in a medical school neuroscience lab with a bunch of grad students and postdocs. Everyone has a Mac laptop, paid for by the lab. Two postdocs have MacBooks. Everyone else has a MacBook Pro. Except the PI who runs the lab, who has an MBA. The only one in the lab. He values small size and weight more than anyone else. He also travels more than anyone else.
I don't see many MBAs around campus.
Likewise when I went to the student union to grab some dinner. Hundreds of students all with laptops open, a handful of Macs. I'd say at rates about at the same as market penetration...~10%.
It may be a geographic thing. Certain regions may make MBPs more appealing, or certain schools may subsidize the purchase more. I've noticed similar rates at other schools in the area.