I agree that super glue is often brittle on plastic, but with some plastics, the plastic actually appears to "melt" together as you're applying pressure. When this happens, you know that the bond will be very strong. From my experience, Mac cases are this type of plastic. I had a latch break off of a 6100. These take a lot of pressure and mine has not broken again.

JB Weld is amazing stuff, but it always leaves at least a tiny gray mark whereas super glue is clear.