Define Dragging: on a trackpad, tap and then move your finger to "drag" the item you tapped on (so tap and hold, slide).
After several searches, thinking my google-fu must be slipping I found it!
It's as simple as opening System Preferences, go to Universal Access » Mouse & Trackpad » Trackpad Options and enable 'Dragging (with/without) Drag Lock' (the second checkbox) to restore the old behavior.
I am sooo happy to have found this because the few days it wasn't working on my iMac enflamed my carpal tunnel, a lot.
No back to mourning the loss of Steve Jobs... :-(
