Well, it costs about the same as a quality regular pillow, so if you like it, it's not a bad value.
Note the fine print: "Claims for MyPillow® are based on medical opinion and user experience and not on actual clinical studies."
Which, again, is no big deal. But it's just a pillow.
Me, I get two of the softest down pillows I can find, and one super firm. I set one soft on top of one firm, and I use the second soft to support my arm, and to swap out with the first one every week or so.
MyPillow is cheaper than that, FWIW; those down pillows go about a C-note each in King size. But I like what I have.
Anyone who gets MyPillow, please report.