Catherine is so feminine, princessy and beautiful tonight, I always loved that shade of blue, it always makes a women look younger and it goes well with her skin. About the dress itself, I'm not particulary amazed with that cut and style, as its a bit regular and not to mention that it looks a bit bad made, but overall, it suits Catherine a lot!
Always loved the earrings and I really like her simple yet so pretty hairstyle.
About the shoes, gosh, I have always issues with her shoes. I like them but not for this dress or evening event. A more "polished" and "elegant" shoes would have made it perfect. However, it doesn't look horrible either, so I'll not complain much.
As I thought, pregnancy makes Catherine shine in Dresses. A true beauty, LOVE her.