Click here for a great review of the "David Tennant era of Doctor Who" in the Toronto Sun (as they call it).
One quote from the article is "So what did Tennant bring to the series? Intelligence, talent, bravado, quirky humour and the good sense to know when it was time to pass the torch — and relieve the burden of being a renegade Time Lord."
And the article ends with "So Tennant’s legacy is huge. Matt Smith has big shoes to fill."