It is perhaps on the 'mature' side, but I really do like Catherine's dress from the luncheon. It was a classic, feminine piece in a lovely color, although perhaps not Catherine's best shade, and well tailored. She really does wear pleats well.
The jewellery looked lovely – I found it exciting to see her in a brooch. For me, the shoes were just ok.
Her hair and makeup were typical, and yes I would have liked to see her with her hair up or pulled back so that the neckline would be better displayed and the jewellery shown off. (For me, it is not about a dislike of her hair, or being in the 'hair up' or 'hair down' camp; it is no more sinister than a case of what style I would like to see with a particular outfit, just like I might like to see certain accessories with a given outfit.)
All-in-all, Catherine looked elegant, very understated and, most importantly, very appropriate for the event.