I prefer these corners because they're more adjustable, and easier to adjust—you don't have to remove the glass. In addition, the heat spreader on my printer is slightly larger than the glass. The stock corners would secure the spreader, but there was still some play with the glass. Not good. These corners have a slight overhang that allows for a larger spreader, but still secures the glass. Also note that once in place, you don't have to hold the nut while you loosen or tighten the upper screw because the nut sits recessed into the bottom part.

Inspired by a set of corners made by "hellphish" but not derived from it.

Update 2013-03-22: Added a 4mm hole for a leveling set screw.
Update 2013-03-28: Made a 4.1mm hole behind the screw so it's closer to the edge of the heat spreader, so it won't damage the kapton heater.