Does keyframe slow move exist? I remember, in Dope Sheet, using Shift while dragging keyframes (I always use G) to be more precise. With 2.7, that doesn't work. I tried with 2.66... and it neither! Tried 2.57... and neither.

Am I wrong and this function never existed... or there was a version that supported it?

EDIT: I don't want to move to decimal frames (eg: 24.534). As commented, I want to move keyframes in a zoomed-out-view and be precise when dropping them.
When the new animation system was added, Auto Snap was enabled by default in the Dope Sheet and Graph Editor. It uses the nearest frame for snapping. You can change this behavior using a the Auto Snap dropdown menu in the header (it's in both the Dope Sheet and the Graph Editor). You can disable Auto Snap altogether by setting that dropdown to "No Auto-Snap".