OS X - How do I remove photos from my iPhone using the Photos app after import?
I'd go for the 'not quite cave-man' approach - though still a bit manual...

Launch Image Capture.

Plug in iDevice

Select any/all photos you wish to delete

The Delete button is at the bottom of the window [the 'no-entry' sign]


After comments - the button is still there in Yosemite.
Update Nov 2015 - the button is still there in El Capitan, though it is now black &amp; white, not red.
Picture updated to Image Capture 6.7 after further queries on the button not being there.
Update July 2016, as people are still missing this bit...
If the Delete button doesn't appear, eject &amp; re-plug the phone.