My upper case also came off with a little difficulty. There are some plastic tabs that hold the case down (4 of them). They sorta "pinch" onto 4 little bars that are part of the upper case (note, the bars appear to be metal). I worked my upper case to the left a little and it came out easier. One of the these tabs was really tight. Note: if you do this, one or more of the tabs may stay on the upper case, you'll need to move them back in place before putting the upper case back on (pry it off the upper case with a spudger, or very carefully with a flat screwdriver as to not damage it). It will slide back into a slot on the body.
My upper case also came off with a little difficulty. There are some plastic tabs that hold the case down (4 of them). They sorta "pinch" onto 4 little bars that are part of the upper case (note, the bars appear to be metal). I worked my upper case to the left a little and it came out easier. One of the these tabs was really tight. Note: if you do this, one or more of the tabs may stay on the upper case, you'll need to move them back in place before putting the upper case back on (pry it off the upper case with a spudger, or very carefully with a flat screwdriver as to not damage it). It will slide back into a slot on the body.