Anyone tried the Gokhale Method for posture?

[GreenBirdy]

Has anyone followed this and had success? I can't work out if it's a bit of a... fad?!

I know my posture is bad when I sit and I get a very stiff upper back by the end of the working day. The wedge cushion they sell is also on small offer on Amazon so wondering if it's worth it - anyone got one?