I've had problems with PEI sheets "pulling up" from the underlying steel sheet, and I was hoping that the added stiffness of the carbon-fiber layer in this plate would prevent that. It does. Even after printing a bunch of warp-prone PA/PC parts the plate remains dead flat. It works as advertised.
w.r.t. the review complaining that it's not a solid CF plate, you wouldn't want one. For starters a 100% CF plate wouldn't stick to the heating plate. Second, it would be prone to chipping and cracking due to CF's lower toughness in relation to steel