I did check in here first, as my OP said
When I'm on the right (small) side of the cassette, down(left)shifting is easy, upshifting doesn't wanna go. When I'm on the left (big) side of the cassette, upshifting is a snap, but for downshifting I gotta push the shifter a little past and give it half a rev or so to catch. This implies to me I've got a gap between the spider and the individual cogs.
But early responders apparently didn't recognize the classic signs of hanger misalignment.