I'm not a big fan of Adobe Illustrator requiring an extra click to set one object as a "key object" to keep it locked in place for other objects to align to it. The feature is better than nothing. Illustrator didn't always have that key object capability.
IMHO, either the first or last object added to a selection should automatically stay locked in place for alignment tasks. That would make the process go a little faster, like it does in CorelDRAW. Illustrator doesn't have comparable align/distribute keyboard shortcuts like CorelDRAW, so the align process can go only so fast. I only see limited value in Illustrator's default object alignment behavior -the stuff that happens when aligning objects without clicking a key object. Aligning objects left, right, top or bottom at least predictably aligns objects to the far object on one of those four directions. But when the objects are center-aligned, either vertically or horizontally, all the selected objects are moved to a unpredictable new location. I don't like that.