I'm personally finding that Keyboard Maestro has some key advantages over other launchers:

1. Simple HUD's - if you group your macros for a particular application into sets of 9 or less, and assign them all the same keystroke in KM5, a little list of their names will pop up when you use that keystroke in that application. You can make the subchoice with keys 1-9,
2. richer dialogs than Applescript's Choose list and Display dialog - multiple fields and buttons,
3. its own variables and flow-control structures.

(Greg Jones gives an example of DevonThink to OO3 cross application use).

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