Hi there,
This is driving me crazy too. I'm on 10.8.5 right now.
System prefs > Keyboard > Keyboard and uncheck " Use all F1, F2 etc...." works but breaks all the single-key functionality on the rest of my keybaord.
There seems to be no option where I can:
1. Retain all the special one-press functionality of the other F-keys (volume, brightness, etc)
and
2. have pressing the F4 key take me directly to the dashbaord
Instead I'm stuck with either having the totally useless Launchpad come up, placing another layer between me and my need for quick access to my calculator widget, or having Dashboard come up but it taking a two more steps to lower the volume of my Mac.
Is there any way I can have my cake and eat it too, or am I stuck wishing for the simpler days of OS 10.6?