Position elements relative to artboards.
Since several improvements to artboards are in the pipeline, I think It would be worth considering positioning elements relative to the top left corner of the artboard. I haven't found a good use for keyboard entry of x and y positions. Positioning elements relatively would make it relatively easy to maintain padding / grids across multiple artboards by entering an exact value.
you can already do that for the current artboard. view>rulers>change to artboard rulers
+1 on keyboard shortcuts related to Alignment