While this is a nice dress, my opinion is it looks nothing like anything Kate would wear. Also reminds me of a much older persons look it puts me in mind of PM gown with the shape of the neck. I would love to see Kate in something more like this:
http://media.onsugar.com/files/2011...b92be2eaa_wedding_dress_with_lace_sleeves.jpg
Yes, I agree with you, the other dress is lovely but looks a bit mature for Kate, IMO. I think something similar to the one you posted would suit her better - I've been hoping she'll do something with lace sleeves.