I used JD on my previous Android phone. I found I was too proactive switching off mobile data and had issues sending MMS messages (which I discovered require data). In my normal area, I didn't find the 3G radio to be that much of a battery hog, so I learned to leave it enabled.
Much depends on the environment of the individual user. If in a fringe area, the radios may boost the power needed to acquire/maintain connections depleting the battery more rapidly than someone in a good coverage area. For me, JD does not provide any significant benefit to my GS4 in my normal travel area.
Also, I have Battery Guru installed which I believe is supposed to function in a manner similar to JD.