I like Pippa's dress. Very classic and classy rather than the ubiquitous strapless/mermaid jobs. I suspect part of the brief for the dress design was to incorporate an a-line skirt to cover her bum. She's got great toned arms so can carry the cap sleeves and the keyhole detail in the back saves the dress from being too severe. I agree with PP that she's likely to change into something more fun and contemporary for the reception.
I like Kate's dress as well; I think it suits her - although I do wish a decent MUA would break in and steal her kohl pencils and give her a intervention-style lesson on how to apply softer liner!
The steal the show picture though has to be Kate shushing the children. I love it - very natural, quite funny and endearing because it's something that happens at loads of weddings when you have young attendants to wrangle manage.