After watching the amazing lecture Cameron Fielding gave at the Pixel Challenge, Reverse Engineering Video Reference. I started using his technique to analize my reference files.
I use a small rig I've created to be able to switch from the "linear" reference to the selected keys.
The bulb at the left holds the frames, allowing you to retime your reference creating holds and speeding up some parts. The right one will hold your keys, set that one to stepped just key your most important frames.
Make sure you set your tangents to linear on the green bulb and stepped on the red bulb.
The cross at the top will let you switch from linear to stepped and it will allow you to also hide and show your reference plane.
You can download the python script here (right click, save as): www.ejoanmiquel.com/ReferencePlane.py
Save the file in your "scripts" folder and then run a python command from maya: