Has anyone used gmatfocus diagnostic ?

Hey puys, has any of you used the GMAT Focus diagnostic provided by GMAC? They are good ?? worth the $$ ? and any idea about the Gmatclub.com challenges ?

Hey puys,

has any of you used the GMAT Focus diagnostic provided by GMAC?

They are good ?? worth the $$ ?

and any idea about the Gmatclub.com challenges ?