According to an article published on Showbiz Cheatsheet, Kate Middleton is one of the most popular members of the royal family per public opinion polls.
There is also an obsession with Kate one day being Queen, though it won't likely be any day in the near future. It is actually Prince Charles that is next in line for the throne, not Prince Willliam. At Prince Charles' side is Camilla. It seems at though the public has forgotten it is Camilla that will be Queen before Kate.