Rectangular selection you can copy or nudge
edited August 2013
Title says it all. Marque selection, then copy (all layer or current layer), or nudge (the existing nudge is great, perhaps reuse that within the selection)
Having a nudge for selected area would be great, although I think it would only applicable on rectangular selections though. If there are no other selection shapes to be used then I don't see why it couldn't be an option (circle, lasso, combine 2 rectangle areas to create a 'L')
Agreed, selections and copy/paste are really important. I have a basic marquee select tool implemented but have to figure out some things to make it work well (how it should work when moving content to and from mapped tiles for example).