I'm now going into the fourth season with the SH Whammy rest. Also I have used all three generations of this rest. Like most rests out there, every year the manufacture comes up with a upgrade (if you wish to call it this) in the design. The whammy is one of those rest.
Unfortunately this year I did not attend the ATA Show and I'm unable to say what's changed on the whammy. Speaking to Cabe a while back, they were thinking of changing the plastic bushings to a ball bearing, as this would give much more support to the launcher armshaft. You will notice there's some movement in the launcher if rocked a bit. This however does 'not' affect the performance, honestly.
One problem the whammy had and this was mainly because of incorrect tension adjustment by the tech setting up the rest. If the cord is too close to the rest, sometimes the trigger spring broke. Spot Hogg beefed up that spring a tad and I have not seen one of those broken since.
The whammy, once tuned properly works really well. It holds thearrow perpendicular to the string all the way thru the let off cycle, but, for about 4 inches. Because itconnects to the cable moving up with the draw cycle, there's no tension, let off, nock travel problems associated with this system.
There are many good rest out the, the LD, the QAD HD are all great rest. For simplicity the WB is hard to beat. It's all a matter of ones choice really.