No, Royal Newbie, Diane von Furstenberg isn't "high fashion". If she were, I wouldn't be able to afford her. The Duchess doesn't wear a lot of high fashion clothes, though she's worn some.
I like the color of this dress, and I like the design of the back, but as I said when she wore it in L.A., the front just doesn't excite me. I find it boring.
I do think it might be nice if she recycled something for the wedding and reception. The paparazzi will be out in force to see what she'll wear, and the attention really should be on the bride.