When I somehow accidentally moved something off grid and then couldn't get it to snap back, I just thought I was doing something wrong, some DP command I didn't know. It would also drive me crazy when I was edge-editing a soundbite and wanting it to snap to the grid line and holding down Command seem to do the opposite of what I would expect. I always managed somehow by zooming and nudging and telling myself I would look this up in the manual when I had time.
Believe it or not, the idea of "relative" snapping never occurred to me as something useful or desirable.

Maybe I just haven't ever encountered a situation where relative snapping would be useful. It's hard for me to envision.
One way or another I have managed to get audio or MIDI where I need it in DP, but I definitely experienced some grid confusion and frustration, most recently in the remix project I just came out of. This thread has definitely given me some things to think about on the topic of grids and snapping.
Babz