It is (1) a statement of status (2) a remark of excellence. (3) a mood or feeling. (Advice: the meaning derives from the tone of voice)
(1) WOW! Your hat is so ferblath! (2) Go Wildcats! You are so Ferblath! (3) OMG, do you see what she's wearing? It's so ferblath!
de Daz C. 05 Decembrie 2008