Not automatically and instantly, like the PanCams, HazCams, and NavCams. With just the one camera, they have to command "shoot" "move" "shoot". They probably don't do that as a standard command, only when there's something interesting.
Edited to remove Qmantoos repeated quote
-- Edited by Chandre on Monday 2nd of August 2010 06:08:35 PM
This article appears to say that the MI gives us two images designed to be used as a stereo pair. Thats interesting and useful.
Snippit... One potential trade-off could affect Opportunity's ability to take stereo images of science targets with its arm-mounted Microscopic Imager camera, rover managers said. Since there is only one imager on the rover arm, Opportunity builds stereo views of targets by shifting the camera slightly to the side. With the shoulder joint locked in a partially deployed position, rover handlers would have to shift Opportunity itself to generate the images, Erickson said.