MIPS works. I had an opportunity to have it proven a couple of months ago, unintentionally.

On a group ride we were split at a railroad crossing. The signal light came on just as we were crossing. I braked hard and stopped just short of the tracks. The train was still about 400 yards away and moving very slowly. As I backed up, just walking backward, the crossing arm came down suddenly and conked me in the head.

As claimed, the Bell Formula MIPS deflected the blow. Nary a scuff or dent in the helmet, and no harm to my admittedly thick skull.

No idea whether that would translate to a typical bike crash. But MIPS does exactly what it's claimed to do.