Lots and lots of info out there already, as well as what's been written above. One thing I will add is that it's not a magic bait. There are times when larger lures will simply outfish the Ned Rig badly. These are usually pre-spawn trips with conditions that most bassers would consider to be ideal - cloud cover, heavy wind, warming trend. Doesn't always happen, but it's been noted by MF regulars several times. It is just another tool for the arsenal, albeit one of the most consistent fish catchers you'll find under the right conditions (i.e., when following directions).
In the sense that a shaky head and a Ned Rig are both just versions of jig-worming which has been around since the 1960s, then you could say they are at least all similar. However, Midwest Finesse (Ned Rig) anglers consider shakyhead fishing to be a form of "power finesse". It uses larger hooks, larger jigheads, and larger baits. It also is based around at least a semi-weedless (Tex-posed) presentation. Midwest finesse is small hooks , small baits, light jigheads, and a generally open hook presentation. To quote Ned:
-T9