I've encountered a strange problem with the snap during transform setting, where it seems to be being ignored.
I've tried toggling it on/off, using the different snap modes (to vertex, edge, face, etc), snap targets, but the behavior that I previously had (being able to drag a vertex towards another and have it snap) seems to have been lost somehow.
I'm assuming I accidentally hit a key combo that changed something but I'm fairly new to blender so I'm not sure what that would be.
Hitting Ctrl seems to move the vertex some units in a direction, but doesn't actually snap it to the nearby vertex.
I should mention that snapping to grid seems to work fine - all other snapping methods do not.