+1 - would be great to implement this in a in the MCP.
Pro Tools has this inside the delay comp display at the bottom of the channel strip. You can click it, type a number (postive/negative) or us click and adjust with the scroll wheel (or by dragging).
Units could still be set via routing pop up - I don't find myself needing to switch between ms and samples often.
Whilst we are at it:
How about a preference to enable playback offset by default? If set to zero it won't affect your tracks so no need to have to enable it in the first place.
Also, please allow for selecting default unit in new tracks (i.e. samples or ms).